Trust AC_SYS_LARGEFILE to provide large file support

Trust AC_SYS_LARGEFILE to provide large file support

AC_SYS_LARGEFILE defines _FILE_OFFSET_BITS in config.h if needed for
LFS, and this automatically maps things like open to open64.  But quite
a few places used explicit 64-bit names, which won't work on platforms
like FreeBSD where off_t is always 64-bit and there are no foo64 names.
It's better to just trust that AC_SYS_LARGEFILE is doing it correctly.

But we can verify this too, as some file could easily forget to include
config.h.  The new tests/run-lfs-symbols.sh checks all build targets
against lfs-symbols (taken from lintian) to make sure everything was
implicitly mapped to 64-bit variants when _FILE_OFFSET_BITS is set.

Signed-off-by: Josh Stone <jistone@redhat.com>