add a few fixes for gcc

fixes #437

src/text/collision.cpp

@@ -166,10 +166,10 @@ float Collision::getPlacementScale(const GlyphBoxes &glyphs, float minPlacementS
                 float s4 = (ob.br.y - nb.tl.y + padding) /
                            (na.y - oa.y); // scale at which new box is to the bottom of old box
 
-                if (isnan(s1) || isnan(s2)) {
+                if (std::isnan(s1) || std::isnan(s2)) {
                     s1 = s2 = 1;
                 }
-                if (isnan(s3) || isnan(s4)) {
+                if (std::isnan(s3) || std::isnan(s4)) {
                     s3 = s4 = 1;
                 }
 

src/text/rotation_range.cpp

@@ -95,7 +95,7 @@ rotatingRotatingCollisions(const CollisionRect &a, const CollisionRect &b,
     std::vector<float> f;
     for (size_t i = 0; i < c.size(); i++) {
         // Check if they are close enough to collide
-        if (!isnan(c[i]) && d_sq <= e[i]) {
+        if (!std::isnan(c[i]) && d_sq <= e[i]) {
             // So far, angles have been calulated as relative to the vector
             // between anchors.
             // Convert the angles to angles from north.