mn10300: relaxing vs section merging

[DJ Delorie]

> Of course, the answer was right after the incomplete comment that
> distracted me :-)

Right.  Just forgot to do a final save before diffing that comment.

The problem I've run into is that we want to fixup relocations that
happen in SEC_CODE segments, regardless of where they point, but NOT
fixups that happen in non-code segments.  Unfortunately, fixP's don't
have a reference to where they're coming from, just where they're
going to.

I'll run C++ tests.