Support `expect!` declaration in Racc grammar file

[yui-knk]

expect warns the difference between expected S/R conflicts count and actual count however racc command exits with success. racc command will exit with failure if expect! declaration is specified therefore build process of racc user will also fail.

[yui-knk]

I will change to implement error_on_expect_mismatch declaration to manage exit code instead of expect! declaration.