aplay,axfer: Replace off64_t with off_t

aplay,axfer: Replace off64_t with off_t

Also replace lseek64 with lseek.

_FILE_OFFSET_BITS=64 is passed to needed platforms since configure uses
AC_SYS_LARGEFILE macro. Therefore off_t is already 64-bit and lseek is
same as lseek64.

Additionally this fixes buils with latest musl where these lfs64
functions are moved out from _GNU_SOURCE and under _LARGEFILE64_SOURCE
macro alone. This makes the builds fail on 32-bit platforms even though
default off_t on musl is 64-bit always.

Fixes: https://github.com/alsa-project/alsa-utils/pull/183
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>