hotfix: Add new patch to libSDL

Copied libSDL to this overlay and add a new patch to fix building breaks
in libsdl-1.2.15-r3.
Merge branch 'hotfix/libsdl-1.2.15-r3'
Merge branch 'hotfix/libsdl-1.2.15-r3' into develop
Merge branch 'develop'
Merge branch 'master' of https://github.com/jcadam/funtoo-openbox