Make hostname parameter const char *. Added a new "ASCII must not be

Make hostname parameter const char *. Added a new "ASCII must not be

	* glib/gconvert.h: Make hostname parameter const char *.
	* glib/gconvert.c: (g_unescape_uri_string): Added a new
	"ASCII must not be escaped" feature, and some missing error
	checking.
	(is_escalphanum): New.
	(is_escalpha): New.
	(hostname_validate): New.
	(g_filename_from_uri): Don't allow hostnames to include
	escaped ASCII, validate hostnames with the new
	hostname_validate.
	(g_filename_to_uri): Validate hostnames with the new
	hostname_validate.

	* tests/uri-test.c: Updated tests to reflect the hostname
	validation changes above.

	* glib/gdate.c: (g_date_fill_parse_tokens): Remove the
	<ctype.h> include and do isdigit -> g_ascii_isdigit.