interval_subtract

  INTERVAL_SUBTRACT - remove an interval from a larger interval

  I_OUT = INTERVAL_SUBTRACT(I_IN, I_SUB)

  Given a matrix of intervals I_IN = [T1_0 T1_1; T2_0 T2_1 ; ... ] 
  where T is increasing (that is, where T(i)_0 > T(i-1)_0 and Ti_0<Ti_1 for all i),
  produce another matrix of intervals I_OUT that excludes the interval I_SUB = [S0 S1].

  Examples:
     i_out = interval_subtract([0 10],[1 2]) % yields [ 0 1; 2 10]
     i_out = interval_subtract([0 10],[0 2]) % yields [ 2 10]