This is simply magical. \o/
Vendored in khashl.h. I wouldn't have used it if this were the only
place where I'd need a custom hash table, but it should come in handy
for other tasks as well, especially when I get to implementing an LRU
for prepared statement caching.
(Can all be done with Perl HV's, but they're less efficient and more
cumbersome for these tasks)
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