[dmd-internals] Optimizer patch + three other critical patches

[Don Clugston]

This is a trivial regression from the last release.
4578 Regression(2.047,1.062): ICE(cgcod.c): var+arr[]

This register assignment bug was tough. Tracking this one down was a
research project.
4443 Optimizer produces wrong code for || or && with struct arrays

2931 Initialization struct with array from another struct
1678 ref with varargs generates invalid code

This one is a bit less important, but the fix is easy.
1418 tupleof bug on nested classes