Fill hatches on PDF and PS backends.

This matches behaviour with the Agg backend.

Fixes matplotlib#3023.
Fixes matplotlib#6228.

Author: QuLogic

lib/matplotlib/backends/backend_pdf.py

@@ -1190,7 +1190,7 @@ def writeHatches(self):
                 Path.hatch(path),
                 Affine2D().scale(sidelen),
                 simplify=False))
-            self.output(Op.stroke)
+            self.output(Op.fill_stroke)
 
             self.endStream()
         self.writeObject(self.hatchObject, hatchDict)

lib/matplotlib/backends/backend_ps.py

@@ -322,6 +322,7 @@ def create_hatch(self, hatch):
             self._convert_path(Path.hatch(hatch), Affine2D().scale(sidelen),
                                simplify=False))
         self._pswriter.write("""\
+        fill
         stroke
      } bind
    >>