String "dequote" in phobos?

[cc]

Does something to dequote (unquote? or what would you call it?) a 
string exist in the standard library?  I didn't see one in 
std.string, just wondering before reinventing the wheel.

Something like:
```d
assert(dequote(`"foo"`) == "foo");
assert(dequote(`'foo'`) == "foo");
assert(dequote(`"foo's"`) == "foo's");
assert(dequote(`'foo "bar"'`) == `foo "bar"`);
assert(dequote(`"fo\"o"`) == `fo"o`);
dequote(`"fo"o"`); // bad quoting, maybe throw an exception here 
or something?
```