Clamp latitude for conic conformal projection.

The Lambert conic conformal projection extends to infinity along the outer edge
of the projection, and thus the latitude must be clamped either at -π/2 or +π/2
depending on the parallels. Fixes #1802.

d3.js

@@ -4600,7 +4600,12 @@
     }, n = φ0 === φ1 ? Math.sin(φ0) : Math.log(cosφ0 / Math.cos(φ1)) / Math.log(t(φ1) / t(φ0)), F = cosφ0 * Math.pow(t(φ0), n) / n;
     if (!n) return d3_geo_mercator;
     function forward(λ, φ) {
-      var ρ = abs(abs(φ) - halfπ) < ε ? 0 : F / Math.pow(t(φ), n);
+      if (F > 0) {
+        if (φ < -halfπ + ε) φ = -halfπ + ε;
+      } else {
+        if (φ > halfπ - ε) φ = halfπ - ε;
+      }
+      var ρ = F / Math.pow(t(φ), n);
       return [ ρ * Math.sin(n * λ), F - ρ * Math.cos(n * λ) ];
     }
     forward.invert = function(x, y) {

src/geo/conic-conformal.js

@@ -13,7 +13,9 @@ function d3_geo_conicConformal(φ0, φ1) {
   if (!n) return d3_geo_mercator;
 
   function forward(λ, φ) {
-    var ρ = abs(abs(φ) - halfπ) < ε ? 0 : F / Math.pow(t(φ), n);
+    if (F > 0) { if (φ < -halfπ + ε) φ = -halfπ + ε; }
+    else { if (φ > halfπ - ε) φ = halfπ - ε; }
+    var ρ = F / Math.pow(t(φ), n);
     return [
       ρ * Math.sin(n * λ),
       F - ρ * Math.cos(n * λ)