Remove explicit casts from some integer constants, to improve readability

[BarryBo]

Kremlin is careful to produce constant values with predictable behavior, despite ambiguities in C about integer promotion due to sizeof(int) and signed-ness of char.

Examples:

• (uint32_t)1U

• (uint32_t)0U

• (int32_t)1

• (int32_t)0

I think Kremlin could omit the casts in a number of cases, while still being certain that the ambiguous cases are well handled. I believe it is safe for constants < 16 bits in length, where it already emits the 'U' suffix for unsigned, or omits it for signed.

For larger constants, close to sizeof(int) on a 16-bit machine, the explicit casts will still be important.

[beurdouche]

Note that HACL* is running on 16bit platforms through the RIOT operating system.

[msprotz]

what is the data model for these platforms?