use floats when resampling lines to match -js

This fixes many small render test and collision differences.

src/mbgl/text/get_anchors.cpp

@@ -28,11 +28,11 @@ Anchors resample(const std::vector<Coordinate> &line, const float offset, const
             markedDistance += spacing;
 
             float t = (markedDistance - distance) / segmentDist,
-                  x = util::interpolate(a.x, b.x, t),
-                  y = util::interpolate(a.y, b.y, t);
+                  x = util::interpolate(float(a.x), float(b.x), t),
+                  y = util::interpolate(float(a.y), float(b.y), t);
 
             if (x >= 0 && x < 4096 && y >= 0 && y < 4096) {
-                Anchor anchor(x, y, angle, 0.5f, i);
+                Anchor anchor(std::round(x), std::round(y), angle, 0.5f, i);
 
                 if (!angleWindowSize || checkMaxAngle(line, anchor, labelLength, angleWindowSize, maxAngle)) {
                     anchors.push_back(anchor);