[AD] Not freeing resources of non-preserved bitmaps on Android is considered harmful :)

[Max Savenkov <max.savenkov@xxxxxxxxxx>]

I think I found another bug in Android implementation. For some reason, 
in 'android_acknowledge_drawing_halt(ALLEGRO_DISPLAY *dpy)' Allegro does 
not delete resources of bitmap if it has ALLEGRO_NO_PRESERVE_TEXTURE 
flag set. Since in reality FBOs and textures for those bitmaps are 
deleted when OpenGL context is deleted during suspension, this leads to 
corruption after the game is resumed. I'm not very clear on details, but 
somehow OTHER bitmaps may end up corrupted because of this.

I tried commenting out this flag and it seems to make everything better 
:) So unless there is some remembered reason for it being there, I 
propose to strike out this check.

Also, I'd like to question the whole approach Allegro takes to 
suspension/resuming on Android. Why doesn't it uses the same method as 
SDL, which preserves the whole OpenGL context, instead of re-uploading 
bitmaps after resuming? This would eliminate the difference between 
NO_PRESERVE_TEXTRURE and other bitmaps (as it should be with OpenGL) and 
also preserve shaders (which presently has to be re-created as well 
during resuming). This would allow Allegro (or its user at least) to 
save memory by setting NO_PRESERVE_TEXTURE for all bitmaps and not store 
in-memory copy of data. Is there any reason not to do so, or is it just 
a historical decision?