(iOS) Fix runtime issues:
    Modifies libco/armeabi.c to be picked up on iOS.
    Patches it to use posix_memalign if HAVE_POSIX_MEMALIGN is defined as greater than 0.
    Add an alias for co_switch_arm as _co_switch_arm.
    Adds the -marm flag to iOS compile flags, without it co_switch_arm will crash.