glslang accepts function with void parameter and non-void parameter

glslang accepts this shader:

```
#version 310 es

void bar(void) {

}

void foo(void, int x) { // Probably should not be allowed

}

void main() {
foo(5);
bar();
bar(void);
// rejected by glslang; good: foo(void, 5);
}
```

I think "void" in the context of parameters should only be allowed to represent an empty parameter list; I don't think it should accept an additional non-void parameter and ignore the void parameter.

Start by running the supplied shader through glslang and trace the parameter-list validation for declarations and calls involving void. Done means rejecting foo(void, int x) and foo(void, 5) while preserving the valid empty-list forms shown in the example.

Written by the indexing model from the issue text.