Don't reload initialization files when processing multiple files (issue 5874044)

[graham]

This feels like a dangerous change.  Obviously we don't /want/
"bleed-through" of parameters or memory from one file to the next, but I
would be shocked if we don't have any of that right now.  I also have
vague memories of some problems with this in the past.

I guesstimate that not reloading init files will expose 2-5 critical
regressions even after the regtests themselves compile ok.  Note that I
use the word "expose", not "create" or "cause" -- the bugs are there
already.  We'll just get reports dribbling in over a few weeks.

If you want 2.16 to be as good as possible, then speeding up the regtest
compile and exposing those potential bugs is certainly a good thing.  If
you want 2.16 to be out soon, then you may want to consider sitting on
this patch until 2.16 is out.  I'm content with either option.

http://codereview.appspot.com/5874044/