Don't compile any of the alsa audio input code if HAVE_ALSA isn't defined. This mainly removes the --v4l2-alsa option if alsa devlopement headers aren't available.

MacOSX/Framework: Minimizes Package Size. only copy the libraries that the vlc modules need. (Patch by Enrique Osuna).

Adds libgcrypt.m4 for systems running autotools without libgcrypt-dev installed
Prefers tabs over spaces in Makefiles