In the past (IIRC, up to around v24.3) transposing things (chars,
words, sexprs, lines) would always leave the point after the
transposed thing.  This means that I could always use a `C--' prefix
to "drag" the current thing backwards in the same way that the default
action drags it forwards.  This is no longer happenning.

After a few trials the thing that seems to fix it is adding this line
at the end of the `transpose-subr' definition:

    (goto-char (+ (car pos2) (- (cdr pos1) (car pos1))))

To be clear, this is not a backward incompatible change -- it fixes
the *current* incompatible change.

Patch file attached.