find and fix other _FILE_OFFSET_BITS=64 unified headers breakage

[enh]

#332 had mmap, but anywhere where we have an #if defined(__USE_FILE_OFFSET64) around a function that doesn't have an __INTRODUCED_IN, we have a similar problem.

stdio.h:

int fgetpos(FILE*, fpos_t*);
int fsetpos(FILE*, const fpos_t*);
int fseeko(FILE*, off_t, int);
off_t ftello(FILE*);
...
FILE* funopen(const void*,
              int (*)(void*, char*, int),
              int (*)(void*, const char*, int),
              fpos_t (*)(void*, fpos_t, int),
              int (*)(void*));

sys/sendfile.h:

ssize_t sendfile(int out_fd, int in_fd, off_t* offset, size_t count);

unistd.h:

off_t lseek(int __fd, off_t __offset, int __whence);

[enh]

actually, lseek is okay because lseek64 has been here forever too...

[enh]

https://android-review.googlesource.com/354934 fixes sys/sendfile.h.

[enh]

https://android-review.googlesource.com/354857 fixes stdio.h.

[DanAlbert]

Just a heads up: this is going to be in r15 but won't be in beta 1. We've got a bunch of new code in the headers (better FORTIFY support) that requires a Clang newer than the one we have in the NDK right now and the new Clang has some issues with arm5, so we're not taking that update just yet. We should have another update really soon, but it won't be in time for beta 1. Apologies for the inconvenience!