#99 cmake // Replace CMAKE_SOURCE_DIR with PROJECT_SOURCE_DIR

[Sergey Nikulov]

Replaced CMAKE_SOURCE_DIR with PROJECT_SOURCE_DIR.

This will allow to include it++ as sub-project using add_subdirectory(<path to="" it++="">).</path>

ref: http://www.cmake.org/Wiki/CMake_Useful_Variables

Patch attached.
Also can be merged trough https://sourceforge.net/p/itpp/git/merge-requests/1/

[Sergey Nikulov]

Additional patch for doc/doxygen_html.cfg.cmake.in file.

[Bogdan Cristea]

patches applied into master branch.