bootanim: Don't cache textures if they're expected to use a lot of VRAM

bootanimation cached all the textures generated until the animation
was completed.
For Hi-res animations with lots of frames (like the new CM9 anim on
xhdpi devices), this implied using large amounts of video RAM, more
than most devices actually have available, causing the animation to
stall (and in some cases, gralloc to lock up); so if an animation is
expected to use a lot of RAM (rough estimation based on frame size
and number of frames), disable cache entirely and generate the textures
on demand

Change-Id: I65b6358d8ddda4350e1f150034c340b22aba5f27
bootanimation: performance enhancements

This patch implements two simple performance enhancements, which
might benefit devices. They are completely opt-in by setting
the following variables.

  * TARGET_BOOTANIMATION_PRELOAD: will preload the bootanimation
    zip to memory; this is handy on devices where the storage
    might be slow. By preloading it, we get quick access to the
    zip file, and the animation doesn't stutter.

  * TARGET_BOOTANIMATION_TEXTURE_CACHE: allows maintainers to
    force texture cache on/off.

Also fixes the sign warnings related to int / size_t comparison

Change-Id: Ibfd04caf019bcac9ba9f80f8c3eadca397a998d1
bootanimation: fix usage of LOGW

Change-Id: I1d59df9f44f414d80058a532644cbbb40e22c701
bootanimation: allow using RGB565 instead of ARGB8888

RGB565 uses considerably less memory, and together with texture
cache, it allows us to offer a really smooth bootanimation on
not so powerful devices.

Change-Id: I9da8fd7e6a587b5895519dd0983ec9b8f676771b
Merge remote-tracking branch 'cm/kitkat' into kitkat