AC_SYS_LARGEFILE autoconf macro is in use in configure script which will
add needed feature macros on commandline to enable 64bit off_t.
Also replace lseek64 with lseek, since it will be same when
_FILE_OFFSET_BITS=64 is defined on relevant platforms via AC_SYS_LARGEFILE
This fixes build with latest musl, where LFS64 interfaces are moved out
of _GNU_SOURCE feature test macros namespace [1]
[1] https://git.musl-libc.org/cgit/musl/commit/?id=25e6fee27f4a293728dd15b659170e7b9c7db9bc
Signed-off-by: Khem Raj <raj.khem@gmail.com>