*Follow-up r78099,r76275:

*Follow-up r78099,r76275:
**Converted CheckUser to use RL
**Made checkuser.js borrow block.js IP functions to avoid ugly duplication (and fix the IP recognition)
**Added missing backslashes to block.js regex strings and avoided backreferences (which work the opposite of PCRE when referencing an unmatched group)
*Made CU not give a common prefix if both v6 and v4 addresses are on the list