blitbuffer with much more optimized blitting
blitbuffer with much more optimized blitting

this introduces the ability to implement n:m bpp optimized blitting.
This allows for a major speedup. Comes with implementation especially
for from/to 4bpp blitbuffer blitting.

frankyifei/koreader-base,koreader/koreader-base,Frenzie/koreader-base,houqp/koreader-base,NiLuJe/koreader-base,houqp/koreader-base,Hzj-jie/koreader-base,houqp/koreader-base,frankyifei/koreader-base,NiLuJe/koreader-base,apletnev/koreader-base,Hzj-jie/koreader-base,koreader/koreader-base,NiLuJe/koreader-base,apletnev/koreader-base,frankyifei/koreader-base,houqp/koreader-base,apletnev/koreader-base,NiLuJe/koreader-base,Frenzie/koreader-base,frankyifei/koreader-base,Frenzie/koreader-base,koreader/koreader-base,apletnev/koreader-base,Hzj-jie/koreader-base,koreader/koreader-base,Hzj-jie/koreader-base,Frenzie/koreader-base