This is step 2 towards fixing #77548.
In the codegen and codegen-units test suites, the `//` comment markers
were kept in order not to affect any source locations. This is because
these tests cannot be automatically `--bless`ed.
Since #47964 was merged, 64-bit mips started passing all structures
using 64-bit chunks regardless of their contents. The
repr-transparent-aggregates tests needs updating to cope with this.
