[RFA jit v2 0/2] minor refactorings for reuse

[Tom Tromey]

Here's a second revision of my patches to the jit branch to clean up
toplev and timevar uses a bit.  The first revision was here:

    http://gcc.gnu.org/ml/gcc-patches/2014-03/msg00895.html

Compared with that revision, this one hopefully includes the
ChangeLog.jit entries; and I took Trevor's suggestion and renamed the
timevar class to "auto_timevar".

Tom