Make ff_inverse stay with libavutil, and optional copy it to libavcodec.
The ff_inverse table is used by FASTDIV macro, defined in libavutil, but up
to now the table was defined only in libavcodec.
After this change, the main copy of ff_inverse is part of libavutil (just
like FASTDIV), but if CONFIG_SMALL is unset, then a different copy is made
available to libavcodec, to avoid the performance penalty of using an
external look up table.
Dynamic linking works, because the libraries are linked with -Bsymbolic, so
the local copy of the symbol has priority over the external; static linking
works because the table is on a standalone object file in both libraries,
so the linker is able to discard one of the two.
Tested on Linux/x86-64 and Mac OS X/x86-64.
Originally committed as revision 24383 to svn://svn.ffmpeg.org/ffmpeg/trunk