Remove AltiVec vector declaration compiler compatibility macros.

The original problem was that FSF and Apple gcc used a different syntax
for vector declarations, i.e. {} vs. (). Nowadays Apple gcc versions support
the standard {} syntax and versions that support {} are available on all
relevant Mac OS X versions. Thus the greater compatibility is no longer
worth cluttering the code with macros.


git-svn-id: file:///var/local/repositories/mplayer/trunk/libswscale@27344 b3059339-0415-0410-9bf9-f77b7e298cf2