Adding optional clipping to tippecanoe-overzoom (#298)

* Plumb a clip bounding box around through overzoom

* Actually do some clipping

* Add a test

* Fix post-binning clipping

* Factoring out geometry parsing from feature parsing

* Accept a clip polygon argument to tippecanoe-overzoom

* Progress in the direction of polygon clipping

* Fix the wagyu flags. We need intersection, not union

* Remove debug spew

* Clip points to polygon bounds too

* Copy the geometric binning code to serve as intersection-finding code

* Add clipper2 for linestring clipping

* Compiles, but does not actually seem to clip. Hmm.

* Oh, it helps if I actually call the function

* Add clipping tests

* Add missing fixture, and don't crash if it is missing

* Remember to do polygon clipping after binning too

* Fix scaling before post-binning clipping. Add test.

* Remove unused parts of clipper

* Rename for consistency

* Revert accidentally added line

* Clip the clip regions to the tile bounds to reduce their complexity

* Add a test of clipping the clip region down to the tile boundary

* Update version and changelog

main.cpp

@@ -2380,6 +2380,9 @@ std::pair<int, metadata> read_input(std::vector<source> &sources, char *fname, i
 			double want = nearby_ft / 2;
 
 			maxzoom = ceil(log(360 / (.00000274 * want)) / log(2) - full_detail);
+			if (maxzoom < 0) {
+				maxzoom = 0;
+			}
 			if (!quiet) {
 				fprintf(stderr,
 					"Choosing a maxzoom of -z%d for features typically %d feet (%d meters) apart, ",