Deduplicate the code among ports and poll definitions of types
directly from a compiler.
This fixes miscompilation of certain programs that instruct compilers
to generate code for different types. This bug has been detected with
-fshort-wchar in EFI firmware.
Proposed and discussed on a mailing list (twice).
Itanium uses custom !ELF fallback switch, temporarily leave it as it is.
bca8c3ffc4