Update some variable names that are now reserved keywords.

Some keywords have been marked as reserved and error or give warnings for the 1.7 transitional syntax now. See https://forums.alliedmods.net/showpost.php?p=2233252&postcount=220

This fixes those. I wasn't really sure what to rename ``in`` inside the crypt.inc file since I really have no idea what's going on in there.

There's still a deprecated function warning:
``clients.inc(162) : warning 234: symbol "GetClientAuthString" is marked as deprecated: Use GetClientAuthId``

but that's a separate issue, and the only way to resolve it (I think) would be to use a macro if version >= 1.7 to use the new native. (or break pre-1.7 compatibility, but that's obviously not happening)