Stricter input parameters help avoid ugly casting when passing
pointers to immutable protobuf data.
While at it: an int return was dropped from 2 functions whose users
never used the result; one of the return paths was returning an
uninitialized value.
Size_t for portablity and warning supression, misc warnings addressed.
Change-Id: I2d5cbdaf0c9b6c4621a7d397772da13da5dc0943
fbae9f3c30