gty.texi (GGC Roots): Clarify that the list of syntaxes is exhaustive.

gty.texi (GGC Roots): Clarify that the list of syntaxes is exhaustive.

	* doc/gty.texi (GGC Roots): Clarify that the list of syntaxes
	is exhaustive.
	(Files): Improve documentation on generated source files.

	* doc/extend.texi (Translation implementation): Document what
	diagnostics look like.
	(Identifiers implementation): Document that there's normally no
	limit on identifier names.
	(Integers implementation): Document two's complement.
	(Hints implementation): Document that GCC honours 'inline', mostly.
	(Preprocessing directives implementation): Document that GCC
	requires the current time.

From-SVN: r55857