Don't use IN_FLOAT() when calling fabs() since it may clobber errno.

Don't use IN_FLOAT() when calling fabs() since it may clobber errno.

The emacs build shouldn't fail sometimes with an "Arithmetic error:".

Previously Emacs assumed that fabs() would not modify errno
unless there was an error, but that isn't guaranteed since fabs()
has no error conditions.

Origin: upstream, commit: 8e0e7a92f5ae99ce2461fc0f0b606d4cec3efb81
Added-by: Rob Browning <rlb@defaultvalue.org>
Provided-By: Paul Eggert  <eggert@cs.ucla.edu>
Bug: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=11913