Add CMake configuration

The portable build configuration is convenient to build and run examples.
Ignore CMake build subdirectory
Ignore files generated for IDE support
Improve compiler flags setting
GCC 4.3+ is recommended

Apparently, support for the right angle brackets (N1757) is required, which is available in GCC 4.3 or later.
Add missing #include <cstddef> for std::size_t
Include missing memory_file.hpp
Merge pull request #7 from mloskot/fix-gcc-memory_mapped

Add missing #include <cstddef> for std::size_t
Merge pull request #8 from mloskot/fix-gcc-so_524548

Include missing memory_file.hpp
Merge pull request #6 from mloskot/cmake-build

Add CMake configuration