The original patch handled the grow case but not the shrink case. When the
current and new allocation sizes are in different size classes, jemalloc's
realloc will move the allocation when shrinking, not just truncate the existing
one.
Based on work by Jon Coppeard.
Since these are just interpreted comments, there's 0 impact on actual code.
This removes all lines that match /* vim: set(.*)tw=80: */ with S&R -- there are
a few others scattered around which will be removed manually in a second part.
Surprisingly, this was previously not done.
Also, some of this code seems to be incorrect or,
at the very least, wasn't clear what it was trying to do.
