Use XML_PARSE_RECOVER libxml flag during db open also.

Allow database opening of broken UTF-8 encoded XML databases -- only in
KC_DEBUG mode.
XML importing already got the XML_PARSE_RECOVER flag, but in non-debug
mode too.
Consolidate the import behavior, and allow this feature at opening,
also.

(cherry picked from commit 2779d3d580ebf5ab668ffeb3b4a2f95df9bcfb3c)