Returning variable-sized stack data

[ryuukk_]

+1, however the syntax proposed sucks


```D
ubyte[$] get_variable_size_array(int cond) {
     if (cond == 0)
         return [1,2,3];
     else
         return [1,2,3,4,5];
}


// OR

scope(ubyte[]) get_variable_size_array(int cond) {
     if (cond == 0)
         return [1,2,3];
     else
         return [1,2,3,4,5];
}
```