[skip formal checks] LEC passes with Formality

* Improve code generation for smem RW-port wmode port

A common case for these port-enables is

    wen = valid & write
    ren = valid & !write

which the RW-port transform currently turns into

    en = (valid & write) | (valid & !write)
    wmode = valid & write

because it proved `wen` and `ren` are mutually exclusive via `write`.

Synthesis tools can trivially optimize `en` to `valid`, so that's not a
problem, but the wmode field can't be optimized if going into a black box.
This PR instead sets `wmode` to whatever node was used to prove
mutual exclusion, which is always a simpler expression.  In this case:

    en = (valid & write) | (valid & !write)
    wmode = write

* In RemoveCHIRRTL, infer mask relative to port definition

Previously, it was inferred relative to the memory definition causing
the mask condition to be redundantly conjoined with the enable signal.

Also enable ReplSeqMems to ignore all ValidIfs (not just on Clocks) to
improve QoR.

Fixes #756

Add support for ProtoBuf serialization and deserialization

* Add support for additional features in .proto description

Features added: Info, Fixed[Type|Literal], AnalogType, Attach, Params

* Add support for .pb input files

This involves an API change where FIRRTL no longer implicitly adds .fir
to input file names

Match https://github.com/freechipsproject/chisel3/pull/783

This fixes --infer-rw to not expect an argument. After the annotations
refactor, no option was required, but some legacy code remained.

This also updates the test cases to be more correct and not specify an
option to --infer-rw.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

* Update Parser to use ANTLR CharStreams

This removes some unnecessary object creation in String reading and
manipulation

* Remove two unnecessary traversals from Block construction in Visitor

Relying on /tmp as a place for test output will fail on multiuser systems and may fail if multiple instances of tests are running for the same user.

Candidate fix for #749
This adds DefRegister netlist ordering to RemoveWires

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

It does not provide anything over NoTargetAnnotation. Its existence
suggests some significance so removing it for clarity.

Escape raw params using \'

Also minor cleanup to literal construction in Visitor

Useful if you want to find out how a node was reachable and you used a blacklist during the reachability analysis

Add optional argument to verilogToCpp to suppress VCD

This enables the pattern of attaching "through" a wire to give better
Verilog that also works in Verilator

Use WrappedExpression when combining attaches in ExpandWhens
to ensure no duplication of references in resulting, combined attaches

Makes ExpandWhens preserve connect Infos
Also fix Travis regressions

* Switch Yosys back to 0.7 with patch for moved ABC repo
* Add 30 min timeout for LEC tests
  * h/t https://stackoverflow.com/questions/43918874#44007537
* Move Travis building of Verilator and Yosys to prelude stage
* Don't use automatic Travis Scala tests, do it manually

* Collects Infos found for symbols
* Merges multiple sources for symbol into MultiInfo
* Restores these Infos on connect statements.
* Add test showing preserved Infos
* Changed ++ methods on the Info sub-classes
  * Ignore NoInfo being added
  * Fixed way adding was implemented in MultiInfo
* Made InfoMap a class which defines the default value function

* Make VerilogEmitter properly handle pad of width <= width of arg

* Constant prop pads with pad amount <= width of arg

This should close #757. It should also allow for stop() and printf()
to be used with zero-width fields.

Yosys 0.7 build is broken because ABC moved repos and the link no longer
works

Replaces old VerilogWrap which didn't work with split expressions and was
actually buggy anyway. This functionality reduces unnecessary intermediates in
emitted Verilog.

* top wiring transform

* fixup comments

* TopWiring cosmetics

* move prefix into TopWiringAnnotation

* remove test function from transform file

* add ChildrenMap to InstanceGraph API

* use namespaces

* remove wiringUtils from TopWiring pass

* enable multiple output functions

* TopWiring cosmetics, tests and lowform

The following are deprecated in favor of DiGraph/InstanceGraph:
  - firrtl.passes.wiring.Lineage
  - firrtl.passes.wiring.WiringUtils.ChildrenMap
  - firrtl.passes.wiring.WiringUtils.getChildrenMap
  - firrtl.passes.wiring.WiringUtils.getLineage

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

* Change VerilogMemDelays to put new Statements at end of Module

Fixes #547

This is instead of putting them right after the modified DefMemory which could
result in use before declaration errors for things that feed into the new
logic.

* Adds tests that show VerilogMemDelays crashing. (#792)

* Cleaning up BlackBoxSourceHelper - use absolute file paths.
```bash
make[1]: *** No rule to make target `test_run_dir/examples.AccumBlackBox_PeekPokeTest_Verilator345491158/AccumBlackBox.v', needed by `/Users/john/chisel-testers/test_run_dir/examples.AccumBlackBox_PeekPokeTest_Verilator345491158/VAccumBlackBoxWrapper.h'.  Stop.
```
since the path `test_run_dir/examples.AccumBlackBox_PeekPokeTest_Verilator345491158/AccumBlackBox.v` does not exist inside `test_run_dir`.
We should either:
 - strip the targetDir prefix,
 - prepend a `../` to the path,
 - use absolute paths
I decided to go with the latter since this makes the least assumptions about the actual downstream processing and we already use absolute paths in other parts of this code.

* Minor cleanup.
 - Anonymize make failure comment.
 - Use common map syntax.

h/t @sdtwigg

Create sources once per module, not once per instance
Clean up writing the file list
Don't prepend file list with '-v's (non-standard and not all verilog)
Change file list file name (not all verilog)
Use ListSets for determinism

Also make DiGraphTests more ScalaTest-y

It wasn't properly padding the width of the constant zero.
Also add a test that shows the buggy behavior.