[wp/qualif] fix power alt-ergo driver

src/plugins/wp/VCS.ml

src/plugins/wp/share/wp.driver

src/plugins/wp/tests/native.report

src/plugins/wp/tests/wp_plugin/math.i

...lugins/wp/tests/wp_plugin/oracle_qualif/math.0.res.oracle

...lugins/wp/tests/wp_plugin/oracle_qualif/math.1.res.oracle

...lugins/wp/tests/wp_plugin/oracle_qualif/math.2.res.oracle

...lugins/wp/tests/wp_plugin/oracle_qualif/math.3.res.oracle