Force speed irrelevant calls to get/put_symbol() to be noinline.

Force speed irrelevant calls to get/put_symbol() to be noinline.
We need to change decode_line to always_inline because gcc decided not to inline
it anymore once we force some calls to get/put_symbol() to be non inlined and
this decision of gcc would lead to a 10% overall speed loss.
100k smaller object file, no speed change

Originally committed as revision 18673 to svn://svn.ffmpeg.org/ffmpeg/trunk