Remove old file 'compare'.
Change null call to be 0 instead of -1.
Use is_reglike( ).
Handle pseudo-case expressions with no x's, no p's, and 1 body.
Remove launchbury_normalize( ).
We don't need to copy the rotation matrix in exp( ), so don't.
Update.
Only preprocess values if they are full expressions.

This should decrease dynamic_cast< > somewhat?  But not much.
Use assert_is_a( ) in two more places.
Fully convert trees to avoid dynamic_cast in accessing branch lengths!
Decrease memory allocation from H machine hot paths.
Decrease memory allocation in uniquify_reg( ).
Add missing release_scratch_list().
Use scratch lists in find_all_regs_in_context_no_check( ).
Adjust used edges.
Use scratch lists for two more vectors - oops!