plmkstrm: Creates a new stream and makes it the
default 

DESCRIPTION:

    Creates a new stream and makes it the default.  Differs from using
    plsstrm, in that a free stream number is found, and returned.
    Unfortunately, I have to start at stream 1 and work upward, since
    stream 0 is preallocated.  One of the big flaws in the PLplot API is
    that no initial, library-opening call is required.	So stream 0 must
    be preallocated, and there is no simple way of determining whether it
    is already in use or not. 

SYNOPSIS:

plmkstrm(p_strm)

ARGUMENTS:

    p_strm (PLINT *, output) :      Pointer to stream number of the created
    stream.