Drop local lable from ppc asm timer.

The aix assembler does not support local lables.
Rename constant HZ in af_biquads.c as HERTZ.

The aix header sys/m_param.h defines HZ as _HZ.
Rename thread_init() in libavcodec and libavfilter as library_thread_init().

The aix header sys/thread.h contains a definition for thread_init().
Rename constant FRAMESIZE in ra144 codec as FRAME_SIZE.

The aix header sys/mstsave.h defines FRAMESIZE as _FRAMESIZE.
Rename "AVClass class" as "AVClass component_class".

The aix header math.h defines "extern int class()" for C.
Support compilation on aix with gcc.

Shared libraries and the IBM compiler are currently not supported.
"--arch=ppc" has to be passed to configure, uname is not compatible.
Merge remote-tracking branch 'cehoyos/master'

* cehoyos/master:
  Support compilation on aix with gcc.
  Rename "AVClass class" as "AVClass component_class".
  Rename constant FRAMESIZE in ra144 codec as FRAME_SIZE.
  Rename thread_init() in libavcodec and libavfilter as library_thread_init().
  Rename constant HZ in af_biquads.c as HERTZ.
  Drop local lable from ppc asm timer.

Merged-by: Michael Niedermayer <michaelni@gmx.at>