[tlbuild] trial builds for TL'13

[Karl Berry]

    FAIL: tpic2pdftex
    =================
    ERROR: Floating point numbers miss decimal point. Do
      LANG="C"; export LANG
    before calling awk.

Thanks.  I don't seem to have any locale that reproduces the failure,
but it's clear enough.  I changed the tpic2pdftex script to force (and
advise) LC_ALL=C and unset LANGUAGE (and LANG, though that should be
unnecessary), per
http://www.gnu.org/software/gettext/manual/html_node/Locale-Environment-Variables.html.
Let me know if the problems in Slovenian persist ...

(Looking into chktex woes later, out of time for today.  If anyone else
has a chance, that would be great.  Peter is away until April 7.)

k