For large intra frame intervals or for a choice of bit rate that causes
large bits per frame, it possible that while computing number of bits
available in the gop overflow the datatype bounds. For these
calculations use number_t as this offers wider space
Bug: oss-fuzz-63044
Test: avc_enc_fuzzer
Change-Id: Ifee9130f0021f77905aea67832abc044537088e5
Most of them was benign and didn't risk any data race; they
were used for write-only memory during init.
The array as_itt_memtab in ih264e_get_rate_control_mem_tab
could however cause a real data race, if multiple threads
try to initialize an encoder at the same time, since it
used as temporary storage when mapping between different
structs.
Change-Id: I3ca29f0e3be2fad154becc3ee29867e591975a74
