add logging

[lukaszstolarczuk]

it's based on PMDK's logging.

For now it's not working on tests-examples compilation:

...
[ 21%] Linking CXX executable sorted_get_all_gen_params
/usr/bin/ld: CMakeFiles/example-pmemkv_basic_cpp.dir/pmemkv_basic_cpp/pmemkv_basic.cpp.o: in function `pmem::kv::db::open(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, pmem::kv::config&&)':
/home/luke/repos/luke/pmemkv/examples/../src/libpmemkv.hpp:821: undefined reference to `out_init'
/usr/bin/ld: /home/luke/repos/luke/pmemkv/examples/../src/libpmemkv.hpp:823: undefined reference to `out_log'
collect2: error: ld returned 1 exit status
make[2]: *** [examples/CMakeFiles/example-pmemkv_basic_cpp.dir/build.make:85: examples/example-pmemkv_basic_cpp] Error 1
make[1]: *** [CMakeFiles/Makefile2:742: examples/CMakeFiles/example-pmemkv_basic_cpp.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
[ 21%] Linking CXX executable example-pmemkv_open_cpp
/usr/bin/ld: CMakeFiles/sorted_get_all_gen_params.dir/engine_scenarios/sorted/get_all_gen_params.cc.o: in function `pmem::kv::db::open(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, pmem::kv::config&&)':
/home/luke/repos/luke/pmemkv/tests/../src/libpmemkv.hpp:821: undefined reference to `out_init'
/usr/bin/ld: /home/luke/repos/luke/pmemkv/tests/../src/libpmemkv.hpp:823: undefined reference to `out_log'
/usr/bin/ld: CMakeFiles/sorted_get_all_gen_params.dir/engine_scenarios/sorted/get_all_gen_params.cc.o: in function `pmem::kv::db::close()':
/home/luke/repos/luke/pmemkv/tests/../src/libpmemkv.hpp:834: undefined reference to `out_log'
/usr/bin/ld: /home/luke/repos/luke/pmemkv/tests/../src/libpmemkv.hpp:837: undefined reference to `out_fini'
collect2: error: ld returned 1 exit status
make[2]: *** [tests/CMakeFiles/sorted_get_all_gen_params.dir/build.make:87: tests/sorted_get_all_gen_params] Error 1
make[1]: *** [CMakeFiles/Makefile2:1365: tests/CMakeFiles/sorted_get_all_gen_params.dir/all] Error 2
/usr/bin/ld: CMakeFiles/example-pmemkv_open_cpp.dir/pmemkv_open_cpp/pmemkv_open.cpp.o: in function `pmem::kv::db::open(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, pmem::kv::config&&)':
/home/luke/repos/luke/pmemkv/examples/../src/libpmemkv.hpp:821: undefined reference to `out_init'
/usr/bin/ld: /home/luke/repos/luke/pmemkv/examples/../src/libpmemkv.hpp:823: undefined reference to `out_log'
collect2: error: ld returned 1 exit status
make[2]: *** [examples/CMakeFiles/example-pmemkv_open_cpp.dir/build.make:85: examples/example-pmemkv_open_cpp] Error 1
make[1]: *** [CMakeFiles/Makefile2:823: examples/CMakeFiles/example-pmemkv_open_cpp.dir/all] Error 2
[ 22%] Linking CXX executable example-pmemkv_pmemobj_cpp
/usr/bin/ld: CMakeFiles/example-pmemkv_pmemobj_cpp.dir/pmemkv_pmemobj_cpp/pmemkv_pmemobj.cpp.o: in function `pmem::kv::db::open(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, pmem::kv::config&&)':
/home/luke/repos/luke/pmemkv/examples/../src/libpmemkv.hpp:821: undefined reference to `out_init'
/usr/bin/ld: /home/luke/repos/luke/pmemkv/examples/../src/libpmemkv.hpp:823: undefined reference to `out_log'
collect2: error: ld returned 1 exit status
make[2]: *** [examples/CMakeFiles/example-pmemkv_pmemobj_cpp.dir/build.make:85: examples/example-pmemkv_pmemobj_cpp] Error 1
make[1]: *** [CMakeFiles/Makefile2:796: examples/CMakeFiles/example-pmemkv_pmemobj_cpp.dir/all] Error 2
make: *** [Makefile:163: all] Error 2

---

This change is 

[igchor]

Reviewable status: 0 of 12 files reviewed, 1 unresolved discussion (waiting on @lukaszstolarczuk)

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src/libpmemkv.hpp, line 16 at r1 (raw file):

#include "libpmemkv.h"
#include "logging.h"

We don't want to have any logging here - it's the public header and the logging.h/out.h will not be installed, right? Everything should be logged within the library.