[tlbuild] Bug in libpng affecting Solaris 10

[Karl Berry]

    Several years ago, I wrote the script below to display the predefined
    symbols for assorted compilers

Nice.  FWIW, for gcc alone, I've long used this one line (that is in
your script too, vastly generalized :):
  gcc -E -dM - </dev/null | awk '{$1=""; print}' | sort

(Nowadays, yeah, have to set LC_ALL=C.  Sigh.)

Thanks,
K