Update ofxAndroidVideoPlayer.cpp

If the texture is unloaded by "unloadTexture()" method and if the Android app goes then to pause state; when returning to resume state a Fatal Error is occuring because the unloaded (unavailable) texture cannot be reloaded.

Due to this bug I added:

    texture.texData.bAllocated = false;

line to the end of unloadTexture() method.
Update ofxAndroidVideoPlayer.cpp

I put the unloadTexture() method to its old version and I add a new "removeTexture()" method to the code.

ps. The new method has to be added also to the header file.
Update ofxAndroidVideoPlayer.h

I added the proposed removeTexture() method to the header file as well.
Merge pull request #3132 from noyanc/patch-1

Update ofxAndroidVideoPlayer.cpp