clean.pl on Windows fails to remove flex output

Hi folks

I've noticed while testing the VC 2010 patches that clean.pl in 
src/tools/msvc doesn't remove files generated by flex. I landed up with 
a broken configuration while testing my x64 builds that caused the 
creation of zero-size outputs for bootscanner.c etc. These weren't 
re-generated on re-build even after a clean, and because they're in 
.gitignore they aren't flagged as dirty in the tree either. Because an 
empty file is a valid C compilation unit, everything proceeded merrily 
until linkage failed.

Should clean.pl be removing such files? Or, since they're probably 
included in release source tarballs, would a separate "gitclean.pl" be 
required?

--
Craig Ringer