47_OBIS.pm - Workaround for DZG DVS74

[tschaeffer2]

When the 47_OBIS.pm module is used in combination with a DZG DVS74 power meter, the current power value is sometimes interpreted as a negative value. Even if this seams to be bug in the power meter itself if would be very helpful to implement a workaround in the 47_OBIS.pm module. A workaround implementation in C is described here: https://github.com/jmberg/libsml/commit/81c4026e3d94f7a384cdd89f62a727b83269cdec Additional information can be found on this page: https://wiki.volkszaehler.org/hardware/channels/meters/power/edl-ehz/dzg_dvs74

I am sorry that I cannot implement the code by myself. I could help to test the code in combination with my power meter if this is helpful.