gst-plugins-base aarch64 port of neon code

[Riku Voipio]

Gstreamer-plugins-base has a fork of speex resampler, that has optimized neon version for ARMv7. The configure test will attempt to compile ARMv7 neon asm on Aarch64, which will fail during build. Upstream has included a fix that disables NEON on Aarch64:

https://bugzilla.gnome.org/show_bug.cgi?id=712367

Patch accepted by upstream:

http://cgit.freedesktop.org/gstreamer/gst-plugins-base/commit/configure.ac?id=472ded1cf333a35e328a21084f46a28dd5febfef

The fix causes slower performance on Aarch64, so it should be replaced by NEON code that works on both ARMv7 NEON and Aarch64 SIMD. This should be achievable using portable NEON Intrinsics:

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dht0002a/ch01s04s02.html