Use __typeof__ instead of GCC-specific typeof keyword.

Use __typeof__ instead of GCC-specific typeof keyword.
The typeof keyword is disabled by default when building with -std=c99
as it's a GNU extension.
ICC supports the __typeof__ keyword as well as typeof.

Patch by Diego 'Flameeyes' Pettenò %flameeyes A gmail P com%

Originally committed as revision 15527 to svn://svn.ffmpeg.org/ffmpeg/trunk