Fix compile failure introduced by 4d0deaf .

Failure not spotted because you have to already know to run
`perl Configure.pl --maintainer` and
`rm compilers/imcc/imcparser.{c,h}` to regenerate the IMCC grammar;
otherwise `make` will silently not even try to re-compile imcc.{y,l} .

Needs ticket to be opened on this silent issue.
Regenerate imcc grammar.