3.x: Validate argument naming consistency between base class methods

[akarnokd]

Operator argument naming should match between base classes on the same operators.

For example Observable::buffer(boundary) vs. Flowable::buffer(boundaryIndicator).

Source-level comparison would be too complicated so reflection can be used for this, provided the class saves the argument names. Javac 8 has this option that must be enabled in the IDE and in build.gradle:

[compileJava, compileTestJava]*.options*.compilerArgs << "-parameters"

tasks.withType(JavaCompile) {
    options.compilerArgs << "-parameters";
}

An extra test is preferrable to remind users enabling this option:

    void method(int paramName) {
        // deliberately empty
    }

    @Test
    public void javacParametersEnabled() throws Exception {
        assertEquals("Please enable saving parameter names via the -parameters javac argument",
                "paramName",
                getClass()
                .getDeclaredMethod("method", Integer.TYPE)
                .getParameters()[0].getName());
    }

There are some common operator names across all base classes, these should match as well.