InternPool: add an int_u8 value encoding

On a simple input file, this had a total savings of 21% in the
InternPool:

Before:
    int_positive: 427 occurrences, 8975 total bytes
After:
    int_positive: 258 occurrences, 5426 total bytes
    int_u8: 169 occurrences, 845 total bytes
2f9b7dc102Andrew Kelley committed on 6/11/2023, 3:42:29 AMparent4fe0c58
1 file changedLine totals unavailable