* src/ltlvisit/basicreduce.cc: Perform the following reductions.
a U (b | Ga) = a W b
a W (b | Ga) = a W b
a U b | Ga = a W b
a U b | a W c = a W (b | c)
a W b | a W c = a W (b | c)
a U Ga = Ga
a W Ga = Ga
* src/ltltest/reduccmp.test: More tests.