Improve formatting of manuals.

Improve formatting of manuals.

contrib/:
	* texi2pod.pl: Replace @@ before @{ and @}, for @samp{@@}.
	Also escape characters with grave accents, to be fixed ...
	(unmunge): ... here.
	(postprocess): Also handle @/ and @acronym{...}.

gcc/:
	* doc/contrib.texi (Contributors): Allow URL to wrap in PDF
	output.
	* doc/cppopts.texi: Fix markup of index entry.
	* doc/extend.texi (Constructing Calls): Fix markup of
	__builtin_va_arg_pack and __builtin_va_arg_pack_len definition.
	(Conditionals, C++ Comments, Pragmas, Unnamed Fields, Thread-Local)
	(Vague Linkage, C++ Attributes): Fix markup of index entries and
	keywords.
	* doc/invoke.texi (Option Summary): Fix spacing.  Rewrap to
	avoid long lines.
	(C Dialect Options, C++ Dialect Options, Warning Options)
	(Debugging Options, Spec Files, Darwin Options)
	(i386 and x86-64 Options, MIPS Options)
	(RS/6000 and PowerPC Options, Code Gen Options): Fix markup of
	index entries, avoid abbreviations, allow URLs to wrap, avoid
	long lines, avoid overlong pages from long @itemx lists.
	* doc/objc.texi (Garbage Collection): Allow URLs to wrap.
	* doc/standards.texi (Standards): Likewise.
	* doc/trouble.texi (Incompatibilities): Fix markup of index
	entry.

gcc/fortran/:
	* gfortran.texi (Argument list functions): Allow URL to wrap.
	* intrinsic.texi (GETGID, GETPID, GETUID, IMAGE_INDEX)
	(IS_IOSTAT_END, IS_IOSTAT_EOR, NUM_IMAGES, THIS_IMAGE)
	(ISO_FORTRAN_ENV): Fix markup in index entries, and a couple of
	code markups in the text.
	* invoke.texi (Fortran Dialect Options)
	(Error and Warning Options, Directory Options, Code Gen Options):
	Likewise.  Remove @code inside @smallexample.

From-SVN: r164533