plgdiori: Get plot orientation

Get plot orientation parameter which is multiplied by 90° to obtain the angle of rotation. Note, arbitrary rotation parameters such as 0.2 (corresponding to 18°) are possible, but the usual values for the rotation parameter are 0., 1., 2., and 3. corresponding to 0° (landscape mode), 90° (portrait mode), 180° (seascape mode), and 270° (upside-down mode). If plsdiori has not been called the default value pointed to by p_rot will be 0.

p_rot (PLFLT *, output) Pointer to orientation parameter.