poly-v0.8.0

• override Z3's buggy SIGINT handler (after 100ms)
• add -T LO:INC:HI option format
• rename -O OUT-BNDS to -O OBJ-BNDS for uniformity
• disentangle critical points and fallback solver from ival solver
• obtaining all solutions to a problem is now handled in a lazy manner
• splitting intervals no longer skips space between midpoint and next double
• critical points solver only handles linear derivatives
• add option -o OBJ-SPEC supporting arbitrary expressions or the expression
  'Pareto(E1,E2,...)' containing such expressions (Pareto optimization is not
  implemented, yet)
• minor improvements/fixes:
  • simplifier deals with double-neg and unnecessary conj/disj
  • logging
  • fix handling option -c auto
  • report and error on surplus unused arguments
  • empty sequence of solvers
  • ext-solver outputs time to solve
  • print the named outputs (if any)
  • sequence of variables in models is sorted now
  • optimize_EA properly forwards strictness info to obj-range
  • check that none of the objectives is constant on the domain