Updated latexmk to 452c.

>From v. 4.48 to 4.52
  Optimize number of calls to kpsewhich.  This often gives a
    considerable savings of run time when a document includes many
    graphics files that are in a texmf tree.
  Fix bug that if an .aux file is deleted and latexmk is run, the
    wrong number of runs of (pdf)latex was made.
  Fix related problem that latexmk sometimes does too few runs of
    (pdf)latex because of the incorrect detection that a file is only
    read after being written.
  Implement direct support for xelatex and lualatex.  Previously these
    programs were used by configuring the $pdflatex so that the desired
    program is run instead of pdflatex.  There are now configuration
    variables $xelatex and $lualatex to specify the commands used, and
    extra command line options -pdfxe and -pdflua.
  In the case of xelatex, considerable improvement in run time is
    given for documents containing large graphics files.  This is
    because compilation is made first to an xdv file instead of direct
    to a pdf file.  Only when this file is finalized is a single
    conversion to a pdf file made.  (This last step can be especially
    time-consuming for documents that bring in large graphics files.)
  Correct detection for missing graphics files with xelatex.
  Work around LuaTeX line-wrapping bug.
  Update documentation.
  Minor improvements in code and diagnostics.

>From v. 4.52 to 4.52b
  Fix bug introduced in 4.52 that use of bibtex wasn't always detected
    when recorder mode is on.

>From v. 4.52b to 4.52c
  Document $kpsewhich_show variable.
  Make -jobname work with -pdfxe and -pdflua


(wiz)