tt(DEFINECOUNTER) creates a new counter, to be subsequently used by,
e.g, the tt(USECOUNTER) function. tt(DEFINECOUNTER) expects two parameter list:
the name of the counter to create and an optional initial value. By default
the counter will be initialized to zero.
    
    Examples:
        verb(
    DEFINECOUNTER(YEAR)(1950)
    DEFINECOUNTER(NTIMES)()
        )
    See also section ref(COUNTERS).
