NULL vs 0

[Ray Holmes]

The problem here is with the C `bible' and with the C compilers.  NULL
should NOT be defined in the `stdio.h' package as this assumes (de facto)
that there is a common interpretation.  If a generic NULL is to be
recognized it *has* to be done by the compiler, NOT the preprocessor.  Only
the compiler has the info (if it does) to correctly interpret the `current'
meaning of NULL.  The idea that NULL could be something simple, like 0,
doesn't work as we have seen over the weeks.  If there is to be a generic
NULL pointer it MUST be known to the compiler.