BB:dimRect/lightenRect: add missing bounds check when use_cblitbuffer (#648)
BB:dimRect/lightenRect: add missing bounds check when use_cblitbuffer (#648)

Fix segfaults with highlights spanning multiple pages
koreader/koreader-base,koreader/koreader-base,Frenzie/koreader-base,houqp/koreader-base,houqp/koreader-base,Frenzie/koreader-base,koreader/koreader-base,NiLuJe/koreader-base,houqp/koreader-base,houqp/koreader-base,NiLuJe/koreader-base,Frenzie/koreader-base,koreader/koreader-base,NiLuJe/koreader-base,Frenzie/koreader-base,NiLuJe/koreader-base