supp-mps.tex minor bugs found and their fixes

[Ricardo Sanchez Carmenes <carmenes@bioquimica.uniovi.es>]

Dear Hans:

I have found some bugs in supp-mps.tex that are shown when using
this module with plain (i.e., without loading the whole context
package).

The supp-mps.tex file included in your latest beta/cont-tmf.zip
contains a minor bug that shows up when trying to use metapost
from tex->dvips->ps2pdf. The following diff fixes this bug:

diff -u beta/supp-mps.tex fix/supp-mps.tex
--- beta/supp-mps.tex	Thu Aug 30 18:06:00 2001
+++ fix/supp-mps.tex	Sat Nov 10 13:12:08 2001
@@ -545,9 +545,9 @@
 \def\nouseMPbox#1%
   {\setxvalue{#1}%
      {\noexpand\forgetall
       \noexpand\loadMPgraphic{\MPgraphicfile.\the\currentMPgraphic}{}%
-      \deallocateMPslot\currentMPgraphic
+      \noexpand\deallocateMPslot\currentMPgraphic
       \noexpand\placeMPgraphic}}

 \ifCONTEXT \else \let\douseMPbox=\nouseMPbox          \fi
 \ifCONTEXT \else \let\doifobjectssupportedelse=\relax \fi

Additionally, either the beta and the current official releases
of supp-mps.tex try to check the value of \pdfoutput, even from
classic-tex. The following, placed early in the file, may solve
the problem without harming:

% supp-mps.tex checks \pdfoutput, even if undefined!
\ifx\pdftexversion\undefined\def\pdfoutput{0}\fi

And, finally, \startreusableMPgraphic uses the \ifundefined macro,
which is itself undefined! The following addition could solve the
problem:

% \startreusableMPgraphic needs this (yet) undefined macro:
\ifx\ifundefined\undefined
\def\ifundefined#1{\expandafter\ifx\csname#1\endcsname\relax}
\fi

Regards,
Ricardo.