oslc doesn't notice a violation of function output param rules

[lgritz]

Pointed out by Lee, consider this shader:

void g(output float b) {
    b = 1;  // ok, since b is marked as output
}

void f(float a) {
    g(a);  // <--- should be disallowed, a is not output, but the arg of g() is output
}

shader test (output color Out_Color = 0)
{
    float x = 2;
    f(x);
    printf("%f\n", x);
    Out_Color = x;
}

oslc is missing a check somewhere, it should flag this as an error.