Unify gdb putc functions

Now that filtered and unfiltered output can be treated identically, we
can unify the putc family of functions.  This is done under the name
"gdb_putc".  Most of this patch was written by script.

gdb/guile/scm-pretty-print.c

@@ -689,7 +689,7 @@ ppscm_print_string_repr (SCM printer, enum display_hint hint,
 	      if (string.get ()[i] == '\0')
 		gdb_puts ("\\000", stream);
 	      else
-		fputc_filtered (string.get ()[i], stream);
+		gdb_putc (string.get ()[i], stream);
 	    }
 	}
       result = STRING_REPR_OK;