[tlbuild] branch2018 tl rebuild please

[Karl Berry]

Hi everyone - if you have a chance, please recompile from the TL
branch2018. As in:

  mkdir b18
  cd b18
  svn co svn://tug.org/texlive/branches/branch2018/Build/source .
  ./Build ... as usual ...

There's no point in checking out anything but Build/source; there are no
changes anywhere else. It won't work to rebuild from the trunk since
updates to libraries and other destabilizations have already been committed.

The bug fix for xetex (xdvipdfmx) correctly generating PDF text for
ligatures pushed me over the edge. While we were at it, Norbert and I
included the other post-release bug fixes he has been including in the
Debian binaries.

r47469 dvipdfm-x: Fix a bug which causes a segfault with 1/2/4-bit ...
r47476 m-tx 0.63a (which fixes a serious problem on non-standard archs)
r47477 ptexdir: fix a regression for discontinuous kinsoku table  ...
r47506 typo (so changelog patch will apply)
r47625 recover to give tounicode entries for ligatures
r47626 ptexdir: More strict check kanji token

Please commit/let me know as usual. --thanks, karl.