remove some uint64_t casts and use.

We use automatic int->uint64_t promotion where applicable.

(uint64_t should be kept only for overflow checking and memory alloc).

Change-Id: I1f41b0f73e2e6380e7d65cc15c1f730696862125
dec/vp8l: prevent signed int overflow in left shift ops

force unsigned when shifting by 24.

Change-Id: I6f9ca5fa2109e59b1d46a909136384fc6dc8ca0b
Merge "remove some uint64_t casts and use."
Merge "dec/vp8l: prevent signed int overflow in left shift ops"