I assume the "0 == " around columnStringValue.equalsIgnoreAsciiCase in
ODatabaseMetaData::getSchemas (mysqlc/source/mysqlc_databasemetadata.cxx) was
just a thinko, as the latter already returns sal_Bool, not a <0 / 0 / >0 integer
value.

(Rebased atop ce24919c "loplugin, various in
mysqlc", which covered the same warnings, but didn't consider the negated call
to equalsIgnoreAsciiCase to be an accident as I do here (see above), and
accidentally reversed the logic of OResultSetMetaData::isNullable in
mysqlc/source/mysqlc_resultsetmetadata.cxx, I think.)

Change-Id: Ie89cc8ef7c7638d28307a4b240930d387d75b8f2
Reviewed-on: https://gerrit.libreoffice.org/58908
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>