* doc/gcc.texi: Change the font used for @def... commands to a
	fixed width font.
	* doc/extend.texi: Use more logical markup.  Use "built-in"
	instead of "builtin".  Use @deftypefn to mark up built-in
	functions; specify their types in the @deftypefn and not in the
	descriptive text.  Use TeX quotes and dashes.  Add more index
	entries.

From-SVN: r43274