char can be signedness, and using signedness types is dangerous - it can
lead to negative offsets when doing table lookups. We apparently should just
ban char usage.
Blanket wide to all .c and .h files. Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.
Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.
Implement not, shl and shr in mpz library. Add function to create mpzs
on the stack, used for memory efficiency when rhs is a small int.
Factor out code to parse base-prefix of number into a dedicated function.
