compiler/switch_detection.m:
Add conditionally-enabled code to gather statistics about
what happens when a switch candidate has disjuncts left over,
and we test whether these leftovers form a switch on another variable.
(The results show that after 99.91% of switch candidates,
there are *no* disjuncts left over.)
compiler/mercury_compile_main.m:
Invoke the predicate that writes out any statistics we gathered.
tools/switch_depth:
This new summarizes the results.
