Various selective scheduling fixes

[Andrey Belevantsev]

Hello,

In this thread I will be posting the patches for the fixed selective 
scheduling PRs (except the one that was already kindly checked in by Jeff). 
 The patches were tested both on x86-64 and ia64 with the following 
combination: 1) the usual bootstrap/regtest, which only utilizes sel-sched 
on its own tests, made by default to run on arm/ppc/x86-64/ia64; 2) the 
bootstrap/regtest with the second scheduler forced to sel-sched; 3) both 
schedulers forced to sel-sched.  In all cases everything seemed to be fine.

Three of the PRs are regressions, the other two showed different errors 
across the variety of releases tested by submitters;  I think all of them 
are appropriate at this stage -- they do not touch anything outside of 
selective scheduling except the first patch where a piece of code from 
sched-deps.c needs to be refactored into a function to be called from 
sel-sched.c.

Andrey