The neverclaim output by spin -f '(a && XXXX!a)' was not
understood by Spot. * src/neverparse/neverclaimparse.yy: Support "if :: false fi;" instructions. Spin sometimes output these on dead states. Also rewrite the "transitions" rule as a left recursion. * src/tgbatest/neverclaimread.test: Adjust output because of the right->left recursion change, and add two more formula to submit to Spin to test its output.