[Tilesathome] Large multipolygon relation rendering

[Matthias Julius]

It just came up on talk-us that some of the large riverbank relations
imported from NHD are rendered incorrectly by t at h.  One example is
relation 304245.  This is somewhat huge, there are 110 outer ways with
500 nodes each and a couple of hundred inner ways.

AFAICT it is tagged correctly.  There is waterway=riverbank on the
relation and no relevant tags on the ways.  As a bonus, the outer ways
are ordered.  There were a couple of duplicate nodes that I have taken
care of.

How does or/p deal with incompletely downloaded multipolygon relations?
The rendering seems to be OK when there is only one gap.  But, if there
are more osmarender seems to have problems.

Matthias