Fix `HGRevisonInfo >> #date` to return correct date
Oops, due to a wrong format specification, the returned string was
completely bogus! This commit fixes this and makes sure the date
can be then parsed to an instance of a `Date` using
`Date class >> readFrom:`
pushd common
call mingwmake.bat %1 %2 %3 %4 %5 %6 %7 %8 %9
popd
pushd mercurial
call mingwmake.bat %1 %2 %3 %4 %5 %6 %7 %8 %9
popd