This pull request implements mangling for ConstantMatrixType, allowing
matrices to be used on Windows.
Related issues: #53158, #127127
This example code:
```cpp
#include <typeinfo>
#include <stdio.h>
typedef float Matrix4 __attribute__((matrix_type(4, 4)));
int main()
{
printf("%s\n", typeid(Matrix4).name());
}
```
Outputs this:
```
struct __clang::__matrix<float,4,4>
```
