zipalign/ziptime: use ftello()/fseeko().

Even if we were shipping 64-bit Windows host tools (which we still
aren't), this would still be a bug. Windows is LLP64 instead of LP64,
so the long that ftell()/fseek() uses isn't big enough for a 64-bit off_t.

Test: treehugger
Change-Id: I4e24afe811ff9b7d5696887cc5ee92e54e4a3b76