Add const to various variables in the gas sources.

* symbols.c (decode_local_label_name): Make type a const char *.
	* listing.c (print_source): Make type of p const char *.
	(print_line): Make type of string const	char *.
	(buffer_line): Return const char *.
	(title): Make type const char *.
	(subtitle): Likewise.
	(listing_listing): Make type of p const char *.
	* messages.c (as_internal_value_out_of_range): Make type of prefix
	const char *.
	* stabs.c (s_stab_generic): make type of stab_secname, stabstr_secname
	and string const char *.
	* read.c (_bfd_rel): Make type of name const char *.
	* app.c (out_string): Change type to const char *.
       	(struct app_save::out_string): Likewise.

gas/messages.c

@@ -342,13 +342,13 @@ sprint_value (char *buf, valueT val)
 #define HEX_MIN_THRESHOLD	-(HEX_MAX_THRESHOLD)
 
 static void
-as_internal_value_out_of_range (char *    prefix,
-				offsetT   val,
-				offsetT   min,
-				offsetT   max,
-				char *    file,
-				unsigned  line,
-				int       bad)
+as_internal_value_out_of_range (const char *  prefix,
+				offsetT       val,
+				offsetT       min,
+				offsetT       max,
+				char *        file,
+				unsigned      line,
+				int           bad)
 {
   const char * err;