re PR c++/10915 (a not-useful non-avoidable warning:  conversion to a reference to the same type will never use a type conversion operator)

testsuite/
        * g++.old-deja/g++.jason/conversion5.C: Adjust option.
        * g++.old-deja/g++.bugs/900215_01.C: Likewise.

cp/
        PR c++/10915
        * decl.c (grok_op_properties): Warn possible confusing conversion
        only if -Wconversion.

From-SVN: r68303