This fixes >2GiB files with at least API level 21.
See: https://android.googlesource.com/platform/bionic/+/master/docs/32-bit-abi.md
for the gritty details.
* Based on libavformat's things, except we do not care about API
versions or NDKs without unistd.h, which contains all sorts of
things that we utilize.
* Redefines lseek to always point to the 64bit version.
* Redefines fseeko to always point towards an inlined static
implementation that utilizes the 64bit version of lseek underneath.
Jan Ekström
f4c80d4402