Switch the preprocessor over to using the hash table library. On my
system, this improves the runtime of the output of test/pref/macro.pl
from over 600 seconds to 7 seconds.
Macros have an odd mix of case-sensitive and case-insensitive
behaviour, plus there are matching parameters for arguments, etc. As
a result, we use case-insensitive hash tables and use a linked list to
store all the possible isomorphs.
Define a proper hash table library, instead of the current ad hoc stuff
used for both labels and macros. This only implements the actual
library; it is not yet used.
We use a CRC64 as a prehash. This is almost certainly overkill,
although it is rather efficient (except, arguably, the table lookup)
on 64-bit platforms, and not all that bad on 32-bit platforms. All we
really need is a function which produces two independent 32-bit
results which are used as the primary and secondary hash
respectively. Either way, the prehash function is easily replacable
if/when we have a quicker alternative.
