JIT numeric comparisons

One problem: Boolean operations from libjit return 0. Perl's canonical
false is ''. Right now, I'm just returning libjit's 0, but I think the
best trade-off is going to be returning 0 if a numeric type is required,
constructing a string type if a string is required, and
constructing (*sob*) a full Perl scalar otherwise.
Fix cut & paste error: do not emit right value twice in logical or.
Fix dependencies
First version of multi-perl testing tool

Mostly untested (and the test command is untested altogether) and
totally undocumented.

Basically if it can find its cfg file (warning: Will look in
author_tools where my default file is), it'll install the perls listed
there and dependencies into them, then go ahead and install the modules
from our repos also, by doing:

  perl author_tools/jitperls.pl install

Very high verbosity:

  perl author_tools/jitperls.pl -v=2 install

Custom config:

  perl author_tools/jitperls.pl --config=... install

Only one of the perls:

  perl author_tools/jitperls.pl install --perl=v5.18.1-thread

Also has the following commands:

  install (our stuff)
  install_deps (other stuff)
  build_perl (the perls)
  do (run one-liner using given perl)
  test (run tests of our components - currently untested)
More verbose output on dependencies in jitperl tool
More jitperls fixes (test action still mysteriously broken)
Run Build.PL before realclean and other jitperl.pl fixes
jitperls.pl: shell execution-with-perl-path command
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