Update native
Set src/dst alpha to non GL_ZERO in case STENCIL_VALUE_UNIFORM
Merge pull request #4744 from raven02/patch-28

Set src/dst alpha to non GL_ZERO in case STENCIL_VALUE_UNIFORM
Update native: disable EGLConfigChooser on android.

It seems to choose suboptimal mode on several phones.

May cause us to get no stencil buffer in non-buffered, but meh.
Use libpng to load PNGs. Fixes #4689.