Close file descriptors and fix OpenAL issue

unloadSound() did not previously close file descriptors which would eventually lead to a crash when too many file descriptors where open (about 1000 for Raspberry Pi).

OpenAL sources must be deleted before buffers otherwise it will result in **Illegal Operation**.
ofPixels: fix iterators syntax in vs2012
Merge branch 'master' of github.com:openframeworks/openFrameworks
Merge pull request #3172 from wronex/patch-1

Close file descriptors and fix OpenAL issue
Merge branch 'master' of git://github.com/openframeworks/openFrameworks into apothecary-openssl