DMD 2.066, GDC 4.9.1 compatibility and minor fixes / imporvements

I've finished my changes. You can merge them if you want.

DMD 2.066 compatibility, variadic argument syntax
Wrapper structures are assignable, previously const(void*) member prevented this
There wasn't importPath declaration in the dub file, it's added
Verbose configuration added into dub to help upstream modules find leaks
Programs are creatable from binaries
GDC 4.9.1 compatibility
Various fixes and improvements
I have some OpenCL related unit test there: https://github.com/unbornchikken/neuroflow-D

Works well on:

Win/Linux: DMD 2.066, LDC 0.15, GDC 4.9.1