[tlbuild] initial test builds for TL'15 (no commits)

[Karl Berry]

    xetex-bug73.test.diff-1
    -./xetex -ini bug73 || exit 1
    +./xetex -ini -etex bug73 || exit 1

Adding -etex could alter the behavior being tested for.  (I don't know
that it does, but it seems possible in principle.)

   or xetex-bug73.test.diff-2
   -sed 1,2d bug73.log >bug73.out
   +sed 1d bug73.log >bug73.out

I see Peter applied that.  Yes, it's an improvement, although it seems
to me that the test should have worked ok without it.  Whether
restricted \write18 and %&-line parsing are enabled should be the same
for everyone since the test sets up the environment that way. 

Maybe I'm missing something.  Anyway, no matter, as long as it works.

Thanks,
Karl