Deprecate and undocument the FORCE{MMX|SSE|SSE2|SSE3} flags. These were originally...

Deprecate and undocument the FORCE{MMX|SSE|SSE2|SSE3} flags.  These were originally introduced in TurboJPEG/IPP as a way to override the automatic CPU selection in the underlying IPP codec, which was closed source.  They are not meaningful anymore, since libjpeg-turbo provides environment variables to accomplish the same thing and since it no longer necessarily uses x86 SIMD code behind the scenes.

git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1072 632fc199-4ca6-4c93-a231-07263d6284db