SETSTATUS expression , expression , expression

   Synopsis:
      Updates a 'main' window status bar

   Notes:
      Updates a status bar that was added to the 'main' window with an ADDSTATUS
         or ADDCONSTATUS statement.
      The first expression is the status bar's unique number. If the status bar
         doesn't exist, the SETSTATUS statement is ignored, but the number isn't
         an integer, 0 or above, you'll see an error message.
      The second and third expressions should evaluate to numbers displayed in
         the status bar. Any decimal number is acceptable, even negative
         numbers. If these expressions don't evaluate to a number, a question
         mark is displayed in its place.
      After an ADDSTATUS statement, the first number is expected (but not
         required) to be less than or equal to the second one. After an
         ADDCONSTATUS statement, the sum of the two numbers is expected (but not
         required) to be constant, at least in the short term.

   Requires:
      If the script is not being run as a task, the SETSTATUS statement is
         ignored (and no error message is generated). Execution continues with
         the next statement.

   Examples:
      ! Character's health points are at 50%
      ADDSTATUS 1, "HP"
      SETSTATUS 1, 50, 100

      ! Character's energy points are very low
      ADDSTATUS 2, "EP"
      SETSTATUS 2, 0.017, 1

      ! Show a status bar where the two numbers are added
      ! Character has 900xp, and needs 100 more to level up
      ADDCONSTATUS 3, "XP"
      SETSTATUS 3, 900, 100
