Add missing __gnu_Unwind_Find_exidx symbol

Also since __aeabi* and __gnu_Unwind_Find_exidx symbols
were incorrectly versioned in M (android-23) remove them from
the version script for all platform versions <= 23

Bug: https://github.com/android-ndk/ndk/issues/1
Change-Id: I04902aac25a722100fc502600df908bb3a786356
12 files changed