ndk: <unistd.h>: Update for API level 11 + minor cleanup

- Add pread64(), pwrite64(), ftruncate64() for API level 11
- Cleanup declaration of lseek64() to use off64_t instead of loff_t
- Cleanup declaration of prctl() to use variable number of arguments

The cleanups are performed to better match upstream.

Change-Id: Ic9e44c0ea3dc1202d3c3478bdb2b6006e83b08dc
5 files changed