ImportC with typedef anonymous enums

[rmc]

Could we make enums work the way structs do in importC?

For example (example2d.d):
```
import example2;

void main() {
	my_struct param;
	my_enum eopt;
	//param.opts = A; // not okay
	someFunc(param);
	someFunc2(param.opts); // okay

	someFunc2(eopt); // not okay
}
```
Error is:
```
example2d.d(10): Error: function `example2.someFunc2(__tag3 
evalue)` is not callable using argument types `(__anonymous)`
example2d.d(10):        cannot pass argument `eopt` of type 
`__anonymous` to parameter `__tag3 evalue`
```

example2.c:
```
int printf(const char *format, ...);

typedef enum {
	A = 1,
	B = 1 << 1,
} my_enum;

typedef struct {
	int i;
	my_enum opts;
} my_struct;


void someFunc(my_struct s) {
	printf("okay\n");
}

void someFunc2(my_enum evalue) {
	printf("okay2\n");

}


// void main() {
// 	my_struct param;
// 	my_enum eopt;
// 	param.opts = A; // okay
// 	someFunc(param);
// 	someFunc2(param.opts); // okay

// 	someFunc2(eopt); // okay
// }
```