api3: Normalize command names

- lcb_counter3(), lcb_CMDCOUNTER, lcb_RESPCOUNTER,
  LCB_CALLBACKTYPE_COUNTER

- lcb_remove3(), lcb_CMDREMOVE, lcb_RESPREMOVE, LCB_CALLBACKTYPE_REMOVE

Change-Id: Ieb14ed062d20736c4f03e548184bdf976f84d2a7
Reviewed-on: http://review.couchbase.org/39037
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>