Review of std.signal

[ilya-stromberg]

Robert, please add `RestrictedSignal(Args...).strongConnect(void 
function(Args) dg)` method or at least add link to the 
`std.functional.toDelegate` function.
In current situation your example doesn't work (easy to fix via 
toDelegate):

Error: function phobosx.signal.RestrictedSignal!(string, 
int).RestrictedSignal.strongConnect (void delegate(string, int) 
dg) is not callable using argument types (void function(string, 
int))