Add macros and inline functions to mips math_private.h file.

This is a patch to the MIPS math_private.h file to define HAVE_RM_CTX and
implement the ctx macros.  I also defined a few other macros and inline
functions that I skipped the first time.
Fix two spaces after sentence.

Minor formatting fix that was carried by issuing
sed -e"s/\. \([A-Z]\)/.  \1/" followed by editing result.