[libc] {u}lkbits broken on riscv32 (#115799)

- Re-enabled ulkbits and lkbits for Risc-V
- Bumped `int_lk_t` to a `signed long long` and a `uint_ulk_t` to an
`unsigned long long` to guarantee they both fit in 8 bytes, which `long
_Accum` and `unsigned long _Accum` are defaulted to on 32bit
architectures.

This is probably inconvenient on systems that have a word size larger
than 64 bits?

#115778

GitOrigin-RevId: 13ced90b007fdab3d0ecbe032ead2650d3e7717e
2 files changed