This allows for -fms-extensions to work the same on LP64. For example, _BitScanReverse is expected to be 32-bit, matching Windows/LLP64, even though long is 64-bit on x86_64 Darwin or Linux (LP64).
Implement this by adding a new character code 'N', which is 'int' if the target is LP64 and the same 'L' otherwise
Why not just LP64? Seems arbitrary to make this Darwin sensitive.