Rename: lcb_connection_* => lcbconn_*

Note that the 'struct lcb_connection_st' has not changed because it's
declared inside the headers.

Change-Id: Ie1c2f8e46e936aa2c12b0ef9dbdb80d2542e49d8
Reviewed-on: http://review.couchbase.org/33600
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>