pl_setcontlabelparam: Set parameters of
contour labelling other than format of numerical label

DESCRIPTION:

    Set parameters of contour labelling other than those handled by
    pl_setcontlabelformat. 

SYNOPSIS:

pl_setcontlabelparam(offset, size, spacing, active)

ARGUMENTS:

    offset (PLFLT, input) :    Offset of label from contour line (if set
    to 0.0, labels are printed on the lines).  Default value is 0.006. 

    size (PLFLT, input) :    Font height for contour labels (normalized). 
    Default value is 0.3. 

    spacing (PLFLT, input) :    Spacing parameter for contour labels. 
    Default value is 0.1. 

    active (PLINT, input) :    Activate labels.  Set to 1 if you want
    contour labels on. Default is off (0).