Fix random SIGSEGV errors in native blur

blur.c was allocating large variable length arrays. GCC places these
arrays on the stack, and they were overflowing the stack. By moving
these arrays to the heap, we should avoid this error.
move to latest build tools in gradle
Re-enable native blur in BenchmarkActivity
Merge pull request #9 from Dr-Emann/fix-segfault

Fix Segfault errors