Allocate enough memory for extra-info descriptor
When we added directory byte histories in db94b7f4, we didn't extend the extra-info descriptor size. We allocate 8332 bytes for bandwidth histories in rep_hist_get_bandwidth_lines(), but only 8192 bytes for the total extra-info descriptor in router_rebuild_descriptor(). We should extend this size to 16384 bytes. Bug found by boboper.
See branch extrainfosize in my public repository that should be merged into maint-0.2.2 and master.