catch_errors() takes PTR argument/func instead of char* argument/func.

Update breakpoint.c.
Fix (?) cover_target_enable_exception_callback().  Wasn't returning a
value.

gdb/top.c

@@ -516,7 +516,7 @@ return_to_top_level (reason)
 
 int
 catch_errors (func, args, errstring, mask)
-     int (*func) PARAMS ((char *));
+     catch_errors_ftype *func;
      PTR args;
      char *errstring;
      return_mask mask;