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.
diff --git a/ir.h b/ir.h
index b3fb06d..ce92420 100644
--- a/ir.h
+++ b/ir.h
@@ -707,11 +707,7 @@
 public:
    ir_swizzle(ir_rvalue *, unsigned x, unsigned y, unsigned z, unsigned w,
               unsigned count);
-   ir_swizzle(ir_rvalue *val, ir_swizzle_mask mask)
-      : val(val), mask(mask)
-   {
-      /* empty */
-   }
+   ir_swizzle(ir_rvalue *val, ir_swizzle_mask mask);
 
    virtual ir_swizzle *as_swizzle()
    {