Implementing Speedlimits

• Add a speedlimit attribute to attr_def.h
• Change osm2navit to write the speedlimit attribute if present (and set the appropriate flag as described above)
• Change routing code to query speedlimit if the "speedlimit present" bit is set and add the speed limit to the segment
• In the graph flooding algorithm, use the speedlimit (together with a configurable factor to raise or lower the actual used speed) instead of the default speed for this segment

Already done:

• Assign a new bit to AF_ for "speedlimit present" (to avoid querying the speedlimit attribute if it isn't present)