Stop trying to update the common return block profile data during return
merging, as it is not yet known which return blocks will become tail calls.
Start updating constant return block profile data during return merging
as this is when we transform the flow.

Update the common return block profile data during return merging in
morph (adding more countss) and when creating tail calls (removing counts).

Update profile consistency checker to handle switches properly and to use
tolerant compares.

Add extra dumping when solving for edge weights or adjusting flow edge
weights to help track down where errors are coming from.

Add new FMT_WT formatting string for profile weights, and start using it
in fgprofile.

handle constant return merges too

Update FMT_WT to %g so we don't see huge digit strings.

Also fix dump output from `setEdgeWeights` and pass in the destination
of the edge.

… have

their counts updated.