Audaspace: Moving audaspace 1.3 into extern.

Deleting the old internal audaspace.

Major changes from there are:
- The whole library was refactored to use C++11.
- Many stability and performance improvements.
- Major Python API refactor:
 - Most requested: Play self generated sounds using numpy arrays.
 - For games: Sound list, random sounds and dynamic music.
 - Writing sounds to files.
 - Sequencing API.
 - Opening sound devices, eg. Jack.
- Ability to choose different OpenAL devices in the user settings.

build_files/cmake/platform/platform_unix.cmake

@@ -135,7 +135,7 @@ endif()
 # Codecs
 if(WITH_CODEC_SNDFILE)
 	find_package_wrapper(SndFile)
-	if(NOT SNDFILE_FOUND)
+	if(NOT LIBSNDFILE_FOUND)
 		set(WITH_CODEC_SNDFILE OFF)
 	endif()
 endif()