android: Backport Android support from druntime
phobos: Look up another directory for libiberty

Android's NDK build scripts seem to have an extra level present here.
build: Make phobos' configure depend on libiberty

The parallel build used in Android routinely failed without this.
android: Special case File.seek

There's no fseek64 on Android, so just cast the value to an off_t. Since
Android doesn't support 64-bit addressing of files anyways, this
shouldn't be a real problem.
android: Use GENERIC_IO, not GCC_IO

Android doesn't support the fget*_unlocked functions, so just emulate
them like on Windows.