[librsvg/librsvg-2.44] Fix rounding error on i386 (#455).

[Federico Mena Quintero <federico src gnome org>]

commit e02cbd62257a870424a62d0f04cc9d4e1059bd66
Author: Olivier Tilloy <olivier tilloy canonical com>
Date:   Wed Apr 10 23:28:20 2019 +0200

    Fix rounding error on i386 (#455).

 rsvg_internals/src/marker.rs | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)
---
diff --git a/rsvg_internals/src/marker.rs b/rsvg_internals/src/marker.rs
index ddc4624e..49362ccd 100644
--- a/rsvg_internals/src/marker.rs
+++ b/rsvg_internals/src/marker.rs
@@ -588,18 +588,15 @@ fn find_outgoing_directionality_forwards(
 }
 
 // Normalizes an angle to [0.0, 2*PI)
-fn normalize_angle(mut angle: f64) -> f64 {
-    if angle < 0.0 {
-        while angle < 0.0 {
-            angle += PI * 2.0;
-        }
+fn normalize_angle(rad: f64) -> f64 {
+    let res = rad % (PI * 2.0);
+    if res.abs() < std::f64::EPSILON {
+        res.abs()
+    } else if res < 0.0 {
+        res + PI * 2.0
     } else {
-        while angle > PI * 2.0 {
-            angle -= PI * 2.0;
-        }
+        res
     }
-
-    angle
 }
 
 fn angle_from_vector(vx: f64, vy: f64) -> f64 {