remove unused SvRefBase constructor

Change-Id: I81991231a2cc0b0c9d8289db8435ef8286f1c2bb
loplugin:unreffun

Change-Id: Idc0f3ef53f48b2e77e4cecbcdbbc44a115c6ec2e
-Wunused-variable

Change-Id: I3a22b16d2449a1cb2eba00164f8fca0fd022bd0a
loplugin:unreffun

Change-Id: Ib64683372d89896e7fbac7ac9acb608c5470531c