fix an unintended behavior change in the type system rewrite, which caused us to compile

stuff like this:

typedef struct {
 int x, y, z; 
} foo_t;

foo_t g;

into:
%"struct.<anonymous>" = type { i32, i32, i32 }
we now get:
%struct.foo_t = type { i32, i32, i32 }

This doesn't change the behavior of the compiler, but makes the IR much easier to read.

llvm-svn: 134969