* src/ltlvisit/reduce.hh, src/ltlvisit/reduce.hh:
Add Reduce_Containment_Checks and Reduce_Containment_Checks_Stronger
flags, and call reduce_tau03.
* src/ltlvisit/contain.hh (reduce_tau03): Make "stronger" the
default.
* src/ltlvisit/contain.cc: Style.
* src/ltltest/reduc.cc: Simplify using the reduce() interface
instead of reduce_tau03.
* src/tgbatest/ltl2tgba.cc: Likewise.  Add -fr5, -fr6, and -fr7
options.
* src/tgbatest/spotlbtt.test: Remove cases using "-c", since its
current implementation is not always correct (and apparently
reduces less than -fr7).