1. Set APP_ABI:=all in almost all samples
2. Enhance hello-jni to report more ABIs
3. Fix warnings
Change-Id: I2851c42b77ef8225e32143d225edcf973633e782
Remove all duplicate platform files, i.e development/ndk/platforms/android-N now
only contains files that are introduced in API level 'N' and not found in level 'N-1'
(This makes it easier to manage independent platform release branches, and makes
platform additions trivial to examine and maintain).
Move samples that depends on features of API level 'N' into platforms/android-N/samples
+ update tests/run-all.sh accordingly
Change-Id: I04c4c67c6c674c1714d5812d461d0524a4f4cfd9
