ir_to_mesa.cpp: Fix missing types on some ir_swizzles.

ir_to_mesa.cpp: Fix missing types on some ir_swizzles.

Debugging this took forever as I only looked at constructors in ir.cpp
to find who wasn't setting up ->type.  I dislike hiding code (as
opposed to prototypes and definitions) in C++ header files, but in
this case I have only myself to blame.