[mkgmap-dev] Polyline base optimisation

Hi Gerd If starting with unsigned deltas in polyline encoding, and attempting to reduce the length by testing reduced x/yBase values, there isn't any point in testing Base-1, as the normal number of bits will be the same (added sign bit) and there will be some overflows. Patch attached to change this - it gives me a very slight reduction in RGN size and might give a performance improvement (I didn't detect any). I've also fixed a couple of log. logic errors and changed minDx/y initial to 0, which is much less confusing because they are symmetric with maxDx/y which do use 0. Ticker