clean up torint.h

[Hello71]

1. these shims do not produce ISO C compliant types, since (u)intN_t are specified to have no padding bits (and that intN_t uses two's complement). the limit macros would also be incorrect in such a case.
2. C99 requires that if the implementation does provide such standard integer types, it must also define the intN_t types.
3. (u)intx_t are available almost everywhere now anyways

[Hello71]

done in #26626