libimobiledevice: remove runtime configure check

configure.ac had a runtime check for large file support that got run
on 64-bit architectures, and all runtime checks must go away to be
cross-compile safe.

Luckily that runtime check was extraneous, so just remove it;
standard AC_SYS_LARGEFILE macro should be sufficient for figuring out
proper settings to get large file support.

Also un-blacklist libimobiledevice, since this problem was the
reason for the blacklist.

Signed-off-by: S. Lockwood-Childs <sjl@vctlabs.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>