Patch for completion-setup-function

[Satyaki Das]

Recently, I noticed the nifty highlighting for the first letter
that differs among the available choices during file completion.
This feature doesn't work perfectly for MH-E folder completion
since the regexp to recognize the root is hardcoded.

The attached patch to simple.el changes this.  If this patch were
applied then I could just bind the variable and make the
highlighting work better in MH-E.

Thanks,
Saytaki

simple.patch
Description: Patch for completion-setup-function