Concurrent map data structure

Make pmem::allocator::allocate() throw exceptions in case of bad
allocation.
Make pmem::allocator::construct() throw exception if it is called
outside of transaction.

Implementation is based on concurrent skip list.
Ref:
https://www.cs.tau.ac.il/~shanir/nir-pubs-web/Papers/OPODIS2006-BA.pdf

tests: report error if binary is not built

Merge stable 1.9 into master

Cleanup CI files

based on PMDK's commit 96db274c7, added:
- '-j' param to coverity command (make)
- necessary vars for coverity script (used for Travis CI)
- Coverity certificate download
- skip for forked repos

And fix cases where binary is not built but test is added.

Add libcxx tests for map

Added mockups in CMakeFiles
Files copied from:
https://github.com/llvm-mirror/libcxx/commit/78d6a7767

and do minor cleanup in docker scripts.

- add skip arguments/flags for PMDK and Valgrind builds
- move env variable settings to the top of the files

concurrent_hash_map: fix free_data()

Setting ptr to null after calling delete_persistent is required to
ensure proper recovery.

bump Valgrind version to newest pmem-3.15

If free_data() was called twice this led to assertion failure and
possible double free.

This patch skips freeing data when tls_ptr is already nullptr.

Apply vcpkg patch for pmdk (stable 1.9)

It's a workaround, until vcpkg issue is fixed:
https://github.com/microsoft/vcpkg/issues/11096

use old vcpkg for pmdk build to work properly

It's a workaround, until vcpkg issue is fixed:
https://github.com/microsoft/vcpkg/issues/11096

Containers: handle exceptions in destructors

Handle possible exceptions in destructor to avoid crash
Add tests for free data function

string swap implementation

Merge stable-1.8 into stable-1.9

swap method for pmem::obj:basic_string and tests for it

Merge stable 1.7 into stable 1.8

Update maintainer of deb package.

Merge stable-1.6 into stable-1.7

Fix hash_map doc_snippet

basic_string: optimize move ctor and assignment

Merge stable 1.5 into stable 1.6