Issue 11403 - functions in std.algo can't be used as pred

Partial fix for 11403:
http://d.puremagic.com/issues/show_bug.cgi?id=11403

This pull allows declaring `any`, `all` and `canFind` with their predicates, but without args. This allows either aliasing them to a new name, or using them as a pred to yet a third function. For example:

```D
alias fun = canFind!"a < b";
if (fun([1, 2, 3], 4))
{...}
```
or
```D
import std.ascii : isWhite;
assert( all!(any!isWhite)(["a a", "b b"]));
assert(!any!(all!isWhite)(["a a", "b b"]));
```