Run tests with PMEM_IS_PMEM_FORCE=1

Merge back changes from stable-1.5

Fix range_snapshotting iterator when snapshot_size == 0

When snapshot_size == 0, no snapshotting should happen. This condition
must be explicitly checked inside range_snapshotting_iterator.

Parameters to iterator should specify range accessible by this
iterator. Before this patch those arguments described the whole
array instead of just the part from start to start + n.

Change implementation of canonical iterators for tests.

Update a docker image build-dependency.

It got transitioned to libunwind-dev in Oct 2014; there's still a compat
alias but using it gets you shouted at.

New version takes iterator type instead data type. This
allows for more flexible usage. For example it is required for
testing pmem::obj::experimental::basic_string where required
iterator type is const char*.

test: remove libcxx vector tests that won't be ported

Update Valgrind to 3.14

fix README list of flags

vector: add methods which change capacity

test: add internal vector test

Add valgrind instrumentation support

Modify vector_private test to work with Valgrind instrumentation.

Add const methods to pmem::obj::experimental::array. 

Make persistent atomic fix

check if vector's copy ctor constructs vector from element's type
copy ctor

Tests for:
- const_at
- cfront
- cback
- cdata
- const version of (r)begin
- const version of (r)end
- const version of range

These operators should be marked const as they do not
modify the iterator.

Add:
- const_at
- cfront
- cback
- cdata

This methods behaves the same as const overloads of at, front,
back and data but can be called on non-const object.

Before this patch all arguments passed to constructor were treated
as lvalue references. This patch fixes that by mainting information
about wheter argument is rvalue of lvalue reference.

Introduce flag parameter to make_persistent(atomic)

fix typo