Update READme.md and include/libpmemobj++/README.md with an
information about containers. Fix compiler requirements.

Update PMDK to test the last defrag fixes

Remove CMake checks for pmemvlt (we require libpmemobj >= 1.7 anyway)

Klockwork and coverity fixes

Merge stable 1.8 into master

compatibility tests: test with 1.8.1 instead of 1.8

And explicitly snapshot my_mask and my_size in clear() and swap().
Those are the only 2 function in which we want size and mask to
be changed transactionally (because they can be called inside
outer transaction).

The exception can only be thrown in case of a bug, so assert this
condition.

structs with manual memory management should provide copy ctor.
Otherwise default generated one will perform a shallow copy and
there will be double free in dtor.

detail::pair: make piecewise ctor not constexpr

It should not be marked as constexpr because it does not
initialize all members directly (but through another ctor).

std::pair piecewise ctor is constexpr only in c++20.

Run find_gdb() in tests/CMakeLists.txt

It fixes regression introduced by bc3438ae.

Disable false-postivie helgrind tests

Disable the concurrent_hash_map_rehash_mock tests
due to intermittent failures (most probably false-positive
reported by helgrind).

Ref: 53c8568c
Ref: #469

Use https:// where appropriate.

concurrent_hash_map fixes

Merge stable 1.8 into master

* std::pair<> does not guarantee stable layout
* we need to have constructor which takes only one value and
  default intializes the second value in pair (it's needed for
  insert which only takes key)

Add more defrag tests

The old version lived in PMDK's space.

Add defrag to concurrent hash map

After introducing defrag() compiltaion of test with 1.8 headers fails.

Set tests' timeout value to 590 secs,
because after 10 minutes the build is considered as stalled by Travis:

"No output has been received in the last 10m0s,
this potentially indicates a stalled build
or something wrong with the build itself."

It's needed to iterate over all internal pointers of basic_string.
It's used in the 'defrag' class for storing all pointers
in the internal list for the defragmentation process.