Abs() macro in sysutil.h is incorrect

[Chris Antos]

boy was this annoying.  it took me a while to track down a bug in my app to
the Abs() macro not working correctly!  maybe this is a FAQ, but it was new
to me.

in sysutil.h, Abs is defined as:

    #define Abs(a) ((a >= 0) ? a : (-a))


Doh!!!!  that's wrong.  the left paren should come after the minus sign, and
there should be parens around the second "a":

    #define Abs(a) ((a >= 0) ? (a) : -(a))


otherwise, then compiler cannot correctly evaluate something like "Abs(foo -
bar)", etc.