[tlbuild] trial builds for TL'13

[Karl Berry]

    BV>     make[4]: *** No targets.  Stop.
    By the way, Makefile in this directory is present, but empty.

Well, that certainly explains why there are no targets.  Thomas had the
same result after my r29490 attempt at timestamp fixing.  Evidently my
appending a blank line to
Build/source/libs/cairo/cairo-1.12.8/Makefile.in caused the generated
Makefile to be empty for whatever reason.  Argh.  Didn't happen for me.

Ok, so I bit the bullet and edited cairo-1.12.8/configure.ac to add
AM_MAINTAINER_MODE (and AM_PROG_AR, which automake told me was needed),
and did reautoconf with our stock versions of the autotools.  Committed
changes in r29491.  So ... please try again, with fingers crossed.  (It
builds for me, which proves nothing, since this whole thing always
worked for me.)

k

P.S. I'll be offline for about 24 hours now.  Peter, I didn't have a
change to make the new entry in cairo-1.12.8-PATCHES, etc. before I had
to go out the door.  Tomorrow, if you don't get there first.