HEAD broken again

[Roman Leshchinskiy]

Hi all,

there seems to be something wrong with the way the RTS handles signals 
when forking. With the current HEAD on OS X, I get a lot of testsuite 
failures of the following form:

Compile failed (status 256) errors were:
i686-apple-darwin8-gcc-4.0.1: Internal error: Virtual timer expired 
(program cc1)

and

Compile failed (status 256) errors were:
collect2: ld terminated with signal 26 [Virtual timer expired]

This only happens when using the stage2 compiler and is 
non-deterministic, i.e., it doesn't happen every time (but it does 
happen more often than not). Apparently, the "virtual timer expired" 
message means that gcc receives SIGVTALRM which the RTS uses, IIRC. I'm 
not sure which patch could have broken this.

Roman