common: simplify names of a few common functions

This just a small cleanup of function names that in retrospect
were badly choosen ;)
'pool::get_root' -> 'pool::root'
'pool::get_handle' -> 'pool::handle'
'transaction::get_last_tx_error' -> 'transaction::error'
'transaction::exec_tx' -> 'transaction::run'

common: move v class to experimental

Added array.cpp example 

Remove unnecessary free in make persistent

- updated CMakeLists in examples.
- added array repo with array.cpp, README, and CMakeLists

Ref: pmem/issues#929

common: remove unnecessary variables from travis.yml

and informations about custom libcxx from include/libpmemobj++/README.md

common: remove tests which use custom libcxx

and all utils for supporting custom libcxx.

If make_persistent fails allocation will be rolled-back due to
transaction abort.

tests: add few more tests to increase pmem::obj:array coverage

and fix building one of the tests.

dont check pkgconfig on windows

Print build type to travis job output

it might be installed.

Fix v constructor to always initialize its state.

Depending on how structure containing v is initialized
runid is intialized or not, which leads memcheck to complain:

Conditional jump or move depends on uninitialised value(s)
   at 0x4E5F3CD: pmemobj_volatile (sync.c:656)
   by 0x10AF36: pmem::obj::v<(anonymous namespace)::foo>::get() (v.hpp:125)
   by 0x10A830: (anonymous namespace)::test_init(pmem::obj::pool<(anonymous namespace)::root>&) (v.cpp:80)
   by 0x10AAC8: main (v.cpp:105)

tests: allow running tests under cgdb from ctest

common: fix array behaviour when its size is zero.

This patch fixes 2 things:
 - Double braced initialization of scalar types is not allowed in C++
   so previous version, where underlying type for zero sized array
   was pointer prevented proper zero-sized array initlizatation.
   (Only some compilers complained about this)
 - Standard states that begin() and end() should return some unique value,
   now it is done by returning address of the array itself. To achive that
   alignment of zero-sized array is equal to alignment of type its holding.
   This approach is also taken by libstdc++.

by specifying env variable.

Limit test execution & dump stack trace when they fail.

workaround for old gcc version issue

Check if "inline" aggregate initialization works for array
class members. Use double braces initialization as a workaround.

test: add support for matching memcheck logs

Provide support for matching memcheck and pmemcheck output files.
Match file should follow pattern:
<testname>_<testcase_nr>_<tracer>.err.match

obj: fix pmem::obj::v<> to match new changes

Required due to the pmemobj_volatile API change.