klayout fails to read CELLNAME S_CELL_OFFSET property on windows when it's value is > 4GB

[stefanottili]

klayout reads > 4GB strict oasis on windows wsl (ubuntu), but not on windows

Unsigned long value overflow (position=9862045010, cell=), in file: a.oas

The irony is that klayout doesn't even use the value of the CELLNAME S_CELL_OFFSET property.

[klayoutmatthias]

I don't have the test case, but I replaced all occurrences of "long" and "unsigned long" by the standard types "int64_t" and "uint64_t", so Windows and Linux builds should behave (mostly) identical now.