known constants at compile time rather than at run time. We have a number
of nasty hacks around the place to cache ntohl() of constants (eg: nfs).
This change allows the compiler to compile-time evaluate ntohl(1) as
0x01000000 rather than having to emit assembler code to do it. This
has other smaller flow-on effects because the compiler can see that
ntohl(constant) itself has a constant value now and can propagate the
compile time evaluation.
Obtained from: Ideas from NetBSD and Linux, and some code from NetBSD