* Changes in IP.php:

* Changes in IP.php:
** Fixed hexToOctet()/toOctet() padding (pad left not right)
** Made hexToQuad() left-pad input (e.g. C -> 0000000C)
** Added isPublic6() function (checked as needed by isPublic())
** Rewrote isValidBlock() to not do flaky and roundabout isArray() check. Works for v6 now.
** Removed toArray(), unused outside IP.php and broken for v6
** Removed toOctet() duplication
** Added new private IPv6ToRawHex() function. Used to make toHex() faster.
** Made some functions private
** Reverted r20435, pointless
** Updated credits
* Changes in IPTests:
** Added a bunch of tests (mostly v6)
** Removed weird array test (especially with toArray() gone) after r76514
** Padding *no* longer needed for hexToX functions - assertion flipped
* CheckUser: removed parseRange6() reference (now private)