Remove the logic that determines at compile time whether or not HAVE_ALIAS

Remove the logic that determines at compile time whether or not HAVE_ALIAS
should be defined.  It was flawed on some platforms (e.g., Darwin & mingw).
Instead, rely on the build system to define it on the compiler command line.

This also reverts ajax's hand-edit to indirect_size.c.  I'll fix that on the
X.org side of things later today.