As said before, this relatively old code could uses some cleanup.
This patch depends on another earlier patch being applied:

        [RFA/ada] Improve is_known_support_routine
        http://www.sourceware.org/ml/gdb-patches/2007-01/msg00208.html

2007-01-07  Joel Brobecker  <brobecker@adacore.com>

        * ada-lang.c (is_known_support_routine): Improve the implementation.

Tested on x86-linux. No regression.
Ok to apply?

Thank you,
-- 
Joel