PRWAITBARNEXT

Low level routine to simplify PRWAITBAR next calls

   COUNT = PRWAITBARNEXT(N,STRING,COUNT)

Update call for PRWAITBAR after initialisation by PRWAITBARINIT.

In case COUNT = 0 it initializes as well and a separate call to  PRWAITBARINIT is not needed.

SEE PRWAITBARINIT