Integrate libpng with NEON optimisation into all Android builds

Notes:
The performance of some functions in libpng would be significantly improved with NEON optimisations. These optimisations allow faster rendering of web pages using less power. Android platform can benefit from the integration of the optimised libpng. libpng optimization is not complete yet and is tracked in https://blueprints.launchpad.net/linaro-multimedia-project/+spec/linaro-mmwg-png
[dzin 2011/10/28] Tony to determine the status from Chao and how to proceed.
[mansson 2011-10-28] This BP is about the Android Integration of NEON libpng when finished by the MMWG, but the work on the library is not completed. Set to BLOCKED and moved to 11.11.

Headline:
A NEON-optimized libpng has been itegrated in all builds.

Acceptance:
Android image delivers the optimised libpng by default, working same way as the old libpng library with performance improvement.

Comment:
libpng and affected modules are committed in
http://review.android.git.linaro.org/#change,836
http://review.android.git.linaro.org/#change,837
http://review.android.git.linaro.org/#change,838
http://review.android.git.linaro.org/#change,839
http://review.android.git.linaro.org/#change,840

Work items:
Integrate generic libpng 1.5: DONE
lc4.11 hacking: Fix libpng 1.5 compatible issues: DONE
Apply libpng optimization patches to Android platform: DONE
Build libpng with patches: DONE
Test the performance and compatibility: DONE
Commit the git to manifests: DONE