if-expressions

[Cauterite via Digitalmars-d]

Here's a little patch you guys might enjoy:
https://github.com/dlang/dmd/compare/master...Cauterite:ifExpr0

It enables this syntax:
int foo = if(asdf: 5 else 6);
equivalent to
int foo = asdf ? 5 : 6;

Here's some other examples which work:

// any number of condition/predicate pairs
foo = if(
     asdf : 5,
     doZxcv(bar) : 90
     else 6
);

// redundant commas and colons permitted
foo = if(
     a : 5,
     b : 90,
     else : 6,
);

// roughly equivalent to
// foo = asdf ? 5 : doZxcv(bar) ? 90 : assert(0);
foo = if(
     asdf : 5,
     doZxcv(bar) : 90
);

Also it doesn't conflict with if-statement syntax, as far as I'm 
aware.


Just a little experiment to learn my way around the parser.