Fix hash map erase deadlock

Add doxygen comments describing namespaces

Update version of PMDK in vcpkg

Update version of PMDK in vcpkg
in order to have the defragmentation feature
(change corresponding to commit bd646ca1).

Update version of PMDK in Docker images

Update version of PMDK in Docker images
in order to have the defragmentation feature.

pandoc is required by the newest PMDK.

Consider the following scenario (where A and B are in the same bucket):
thread 1:		thread 2:
find(acc1, A)
			erase(A)
find(acc2, B)

First, thread 1 takes lock on the bucket and then on element A.
Then, thread 2 takes a lock on the bucket and tries to lock element A
but it can't because thread 1 already locked it - this way thread 2 is blocked.
Next, thread 1 tries to lock the bucket but it can't because thread 2 holds it.
Neither thread can progress.

This patch fixes that by introducing the same algorithm as in lookup/insert.
When trying to lock element in erase we now spin in a loop doing try_acquire and
if we do not succeed after specified amount of time we drop bucket lock and try
whole operation again.

remove dependency to containers in ptr test

Pass TESTS_TBB environment variable to Docker

Remove checking for offsetof error in pmdk

Add TESTS_TBB cmake option

Rename get_program_version to get_program_version_major_minor

Now, we do not include any headers which depend on offsetof (types.h)
so this check is not longer necessary.

Merge changes from stable 1.8

... because it does not get the patch part of the version any more.

add TESTS_TBB cmake option to enable/disable(by default) tests which
require Intel TBB library and add tbb to windows tests

Merge stable 1.7 into stable 1.8

Fix minor comments issues

volatile_state: add missing include

test: fix one type in volatile_state test

Check license only in modified files

It fixes the following compilation error:

In file included from /libpmemobj-cpp/tests/volatile_state/\
volatile_state.cpp:33:0:
/libpmemobj-cpp/tests/volatile_state/volatile_state.cpp:\
In function 'void test_vector_of_elements(pmem::obj::pool<root>&)':
/libpmemobj-cpp/tests/volatile_state/volatile_state.cpp:348:30:\
error: conversion to 'size_t {aka long unsigned int}' \
from 'std::__atomic_base<int>::__int_type {aka int}' \
may change the sign of the result [-Werror=sign-conversion]
  UT_ASSERT(v2_initialized == NUM_ELEMENTS);
                              ^

Make persistent_ptr_base non-template and move to main namespace

with two more cases, explicitly using converting assignment and static_cast.

because it was never used, and probably was erroneous (not re-calculating offset).

Since we want to widely use non-template version of base class it's
better to have it in main (pmem::obj) namespace.
Thanks to that it can be used as a type e.g. in vector to
store pointers of various (template) persistent_ptr elements.

persistent_ptr_base is changed to enable usage e.g. as a generic
parameter for a function requiring any persistent_ptr.
Non-template version of the base class is perfect for that.
Rationale for this change is a defragmentation feature, which will operate on
various persistent_ptr's.

Introduce volatile_state support class