compat: revert to using sqlite's close() function for compat with older distros.
close_v2(), in use before this commit, was introduced as part of sqlite 3.7.14 (2012-09-03), and is as such incompatible with debian wheezy (3.7.13) and centos6 (3.6.20). FTR, Wheezy will be supported until May 2018, and centos6, until November 2020.