backport of Revision 120684 for Macintel into gcc 4.2.1?

[Jack Howarth]

   It also looks like we need...

r120874 | mrs | 2007-01-17 15:12:51 -0500 (Wed, 17 Jan 2007) | 2 lines

        * os_dep.c: Fix i686-apple-darwin9 builds.

in addition to r120801 for r120684 to work. I am also
unclear if I should be regenerating include/gc_config.h.in
as well as was done in r120853. Hopefully these will
suppress the Process_# regressions introduced in gcc 4.2.0
witrh the r120684 backport.
              Jack