make alive executable
fix smt encoding of isPower2
add examples from the blog post
fix bitwidth in test so that it finishes in a sane amount of time
add ERROR: line to test
add xor to constant language
minor cleanups and fix a fixme in PRE preds
add umax constant function
Add function lshr().

Needed by instcombine, but has no obvious infix operator. Used lshr() by
analogy with Z3.
Begin visitXor
More tests

Changes to be committed:
	modified:   tests/instcombine/andorxor.opt