update_web_docs: Handle -r and -d options to generate docs for a release or branch...

update_web_docs: Handle -r and -d options to generate docs for a release or branch in a subdirectory.

	* update_web_docs: Handle -r and -d options to generate docs for a
	release or branch in a subdirectory.  Determine names of G77 news
	and bugs files and contributors file after updated docs have been
	installed, not before.  Don't remove files from a subdirectory.
	Don't generate manuals for gcov (included in the GCC manual) or
	iostream (obsolete).  Do generate manuals for cppinternals, gcj
	and porting.  Update regular expressions for detecting whether
	files have really changed when regenerated.

From-SVN: r40589