lexical ambiguity glitch

[Frank Ch. Eigler]

Hi -

There is a glitch associated with the operators chosen for
pre-processor conditionals: %( %? %: %).  The problem is that the
character sequence %( could also occur in an ordinary expression:
   5%(x-5)
This ambiguity is just like C++'s ">>" vs "> >" markers for closing
nested templates.

What shall we do about this?  Nothing, relying on the generated parse
error message to plop a few spaces in?  Rename %( %) to %[ %], which I
believe is immune?

- FChE