* Make mac/win lookups lowercase'd
* Revert #709 & 81042cc
* Adjust HashPolicy implementation across sourcemod
Basically, in order to implement our own (actual) hash policy in
`PluginSys.h`, we needed to remove the blanket implementation of `hash`
that was used before. Now, each policy must implement `hash` along with
`matches` in order to be used with `NameHashSet`. While this does force
us to change every implementation of policies across the entirety of
sourcemod, it allows core to use flexible implementations of `hash`.
* Remove logic duplication
* Improve lowercase checks
