This used to work by adding a magic prefix to the error message, but it appears
that doesn't work with the GHC 6.6 version of Parsec. It now searches for a
magic substring anywhere in the error message.
It uses // as a delimeter rather than \0 now, since including nulls in Strings
causes problems -- for example, putStr "a\0b" will only print "a".
This implements #DEFINE, #UNDEF, #IF, #ELSE and #ENDIF, macro expansion with
##, and TRUE, FALSE, AND, OR, NOT and DEFINED within #IF expressions, with the
same semantics as occ21.
The macro COMPILER.TOCK is always defined by default, so you can now say things
like "#IF NOT DEFINED (COMPILER.TOCK) ... #ENDIF".
