odd error trying to hack FastString implementation

[Isaac Dupree]

Stefan O'Rear wrote:
> You patched GHC, so the version number (which is extracted from darcs)
> automatically went up.  GHC assumes (incorrectly) that this broke the
> interface format, and is trying to stop you from shooting yourself in
> the foot.

But this was from a clean checkout that only contained HEAD plus those 
patches, using ./validate, and the second time after make distclean 
(which I wouldn't necessarily trust, but the first time I also got an 
error in the same place).

Isaac