Some tests and examples require clang >= 8.0

Fix installing libpmem-*.rpm

Fix removing pkg-config rpm package

Most rpm based OSes use the 'pkgconf' name,
only openSUSE uses 'pkg-config'.

Replace 'libpmem-*.rpm' with 'libpmem*.rpm'.
It fixes following errors on openSUSE:

error: Failed dependencies:
        libpmemobj1 = 1.7-1.suse1500 is needed by libpmemobj-debug-1.7-1.suse1500.x86_64
        libpmemobj1 = 1.7-1.suse1500 is needed by libpmemobj-devel-1.7-1.suse1500.x86_64

error: Failed dependencies:
        libpmem1 = 1.7-1.suse1500 is needed by libpmem-debug-1.7-1.suse1500.x86_64
        libpmem1 = 1.7-1.suse1500 is needed by libpmem-devel-1.7-1.suse1500.x86_64

Change header_features constant to a function in concurrent_hash_map.

Add test with concurrent_hash_map and pmem::obj::string

Remove using namespace from a header

Install pmdk-debuginfo package

Merge pull request #480 from ldorau/common-fix-invalid-TRAVIS_COMMIT_RANGE-in-case-of-non-upstream-repository

common: fix invalid TRAVIS_COMMIT_RANGE in case of non-upstream repository

Add missing --output-on-failure to all ctest calls

Add valgrind instrumentation to concurrent_hash_map

Add -j$(nproc) to make commands

It fixes the following error on Fedora-rawhide:
 error: Failed dependencies:
	pmdk-debuginfo(x86-64) = 1.7-1.fc32 is needed by libpmem-debug-debuginfo-1.7-1.fc32.x86_64
	pmdk-debuginfo(x86-64) = 1.7-1.fc32 is needed by libpmem-debuginfo-1.7-1.fc32.x86_64

TRAVIS_COMMIT_RANGE is usually invalid for force pushes.
Fix it when used with a non-upstream repository
by setting to the following value: $LAST_MERGE_COMMIT..HEAD

The commit fix the issue with concurrent_hash_map_rehash_0_helgrind test

header_features was only declared (not defined) in concurrent_hash_map header.
This means that (until C++17) it can be used only in places where address of
this constant is not needed. In operator != we access one member of header_fatures
which requrires it to be declared. This only fails for some compilers like clang-9
because rest of the evaluate this expression at compile time (this is a compiler
decision whether to do this at compile time or runtime).

Fix this issue by creating function header_features().

segment_vector: fix typo and doxygen comments

test: fix briefs of concurrent_hash_map test files

Merge back changes from stable 1.7

Fix array_modifiers test

Move containers out from experimental

This fixes warnings generated by doxygen.

and expose range_snapshotting_terator as typdef in containers.

There was an assignment instead of comparison in the test.