mprotect, SIGBUS, and SIGSEGV

[David Bremner <bremner@debian.org>]

While working on getting the racket garbage collector working on
kFreeBSD, I (well, really upstream) noticed mprotect was sending
SIGBUS. Recently this changed so that it is sending SIGSEGV.  I'm not
sure what exactly changed, except that catching SIGBUS works on squeeze
and catching SIGSEGV works on current sid. Upstream is happy to patch
for kFreeBSD support, but ideally I'd like to suggest something that
will build and work on both squeeze and sid/wheezy.  Is there any static
way to detect this (some preprocessor symbol?), or do I need to run a
program at configure time?  

Please CC me on any responses,

David