Enable unclassified map tests

self_relative_ptr: fix assignment

Enable unclassified tests ported from LIBCXX

separate doc snippets

Ignore more libunwind errors

On most architectures, libunwind reuses getcontext and setcontext from
the C standard library.  memcheck report errors from these setcontext
calls.
This has been reproduced on ppc64le.

[1] https://github.com/libunwind/libunwind#libc-requirements

unify usage of get_pool()

Singlethreaded radix tree implementation

Also, add doc snippet (BytesView example) to radix_tree.

It reads a sequence of keys from stdin and prints radix in a DOT
format.

Based on: https://github.com/pmem/pmdk/blob/master/src/libpmemobj/critnib.h

It is a data structure that holds sequence of chars within the same
memory as the inline_string data structure itself. It requires
custom allocation logic and a runtime wrapper (accessor) which
is aware of the memory location and capacity.

Exclude self_relative_ptr from installation files

Implementing self-relative pointer

Enable libcxx swap tests

Enable map modifiers tests

Update ndctl

Enable few map.modifiers tests

doc: treat doxygen warnings as errors in developer mode

Add missing operators to detail::pair<> required by libcxx tests

@param should not be used multiple times for the same argument.

doc: add examples/ to EXAMPLE_PATH in doxyfile

concurrent_map: fix typo

Without this, doxygen cannot find doc snippets from examples.

added simple example for string