Android renderer using OpenGL ES 2

[ming]

In 4925:

Re #1790: Use OpenGL textures instead of platform dependent textures.

This revision contains:

• remove the generation of iOS texture (instead directly use OpenGL textures)
• add iOS and Android window type

[ming]

In 4928:

Re #1790: Initial basic implementation of Android OpenGL renderer

To use it, app has to specify PJMEDIA_HAS_VIDEO to 1

[ming]

In 4978:

Re #1790: more Android OpenGL renderer

• Fix RGBA color compatibility
• Add autodetection feature to stop rendering for consecutive failures, such as when app is in the bg
• Allow video stream to be created first and supply the output window later

[ming]

In 5007:

Re #1790: Reinitialize Android OpenGL renderer when there is format change.

[nanang]

In 5014:

Re #1790:

• Removed android_opengl_get_surface() for renderer view setup, Java application can directly supply Surface object as renderer window.
• Added renderer view on pjsua CLI app sample.

[ming]

In 5016:

Re #1790: Misc fixes:

• Fixed crash when trying to set NULL surface
• Fixed race condition between setting surface and rendering
• Fixed crash due to GC of VideoWindow?

[ming]

In 5028:

Fixed #1790: Remove unsupported capabilities and some cleanup

[nanang]

In 5030:

Re #1790: Misc fixes on renderer viewing in pjsua CLI app sample, e.g: handle NULL surface, handle video disabled, cleanup unused codes.

[nanang]

In 5032:

Re #1790: Fixed error build of undefined "ANativeWindow_fromSurface()" when video is disabled.

[ming]

In 5034:

Re #1790: Fixed failed Android OpenGL detection if aconfigure is called with --use-ndk-cflags