C4Network2IRC: Remove call to boost::cref which seems to be unnecessary since C4GUI::Ico_Error is just an integer
cmake/FindAudio: Do not add OpenAL_Library to Audio_LIBRARIES on mac because as a preinstalled framework it is just assumed to be present, and linked via the framework linker flag in the main CMakeLists.txt file
CMake: Rename OpenAL_LIBRARY to OpenAL_LIBRARIES for MSVC to be more consistent with the other platforms.