template warning message that will *never* effect compilation

[monkyyy]

Contracts, the ooness of `std.range.interfaces`, several traits 
are about attempting to control the correctness of templates; I 
say all'y'alls should give it all up entirely make the dumbest 
thing possible. However such code will make terrible, terrible 
template error messages, the more used and nested, the worse 
those error message get

If you add dumby functions currently it will effect trait compiles

```d
import std;
void foo()(){
	static assert(0,"foo is fundmentally incorrect, consider using 
bar instead");
}
void callifpossible(alias F)(){
	static if(__traits(compiles,F)){
		F();
	} else {
		"WARN: this didnt actaully compile, but managed to run".writeln;
	}}
unittest{
	callifpossible!foo;//fails
}
```

Suppose you wanted to add a warning to filter that length "cant 
be defined, consider adding something that caches the output", 
that function will likely work like foo from that example code 
and by having it there your interducing interspersion liability's 
and generate new exciting problems.

---

```d
struct filter{
   throw template length() "filter.length can not be defined";
}
```

add it behind a verbose compile flag, define such code as unable 
to effect compilation; maybe it will make template hell have 
better error messages