Use OpenAL_SOURCE_DIR for the CMake module path and declare the project earlier
Use OpenAL_SOURCE_DIR for the CMake module path and declare the project earlier

The minimum CMake version required is also bumped to 2.6. Patch by Andrew West,
allows OpenAL Soft to be properly built as a sub-project.

rryan/openal-soft,Wemersive/openal-soft,Wemersive/openal-soft,arkana-fts/openal-soft,BeamNG/openal-soft,aaronmjacobs/openal-soft,alexxvk/openal-soft,rryan/openal-soft,aaronmjacobs/openal-soft,mmozeiko/OpenAL-Soft,BeamNG/openal-soft,alexxvk/openal-soft,irungentoo/openal-soft-tox,arkana-fts/openal-soft,franklixuefei/openal-soft,franklixuefei/openal-soft,mmozeiko/OpenAL-Soft,irungentoo/openal-soft-tox