More useful tokens, in particular for each opcode possible. This
makes parsing a simpler task to reason as now we're just checking
against an enum rather than doing a string check in linear time.
It makes more sense to do this at the tokeniser as the local data from
the buffer will be in the cache most likely as the buffer is
contiguously allocated. While it will always be slow to do linear
time checks on strings, when doing it at the parser we're having to
check strings that may be allocated in a variety of different places.
This means caching becomes a harder task, but with this approach we're
less likely to have cache misses as long as the buffer stays there.
As strto(ul|ll) allow the parsing of hex literals of the form `0x`, we
allow lexing of hex literals which start with `x`.
They're lexed into C hex literals which work for strtol.
Though we deal with unsigned numbers internally, it should be possible
to read and manipulate negative numbers through 2s complement. Later
on we'll add support for signed operations via 2s complement, so this
should be allowed.
