Add line-width-zero test which currently crashes.

The crash is described in this bug report:

	Crash in cairo_stroke_extents whe line width is 0 and line cap is ROUND
	(_cairo_pen_find_active_cw_vertex_index)
	https://bugs.freedesktop.org/show_bug.cgi?id=10231

test/.gitignore

@@ -70,6 +70,7 @@ leaky-dash
 leaky-polygon
 line-width
 line-width-scale
+line-width-zero
 linear-gradient
 linear-gradient-reflect
 long-lines

test/Makefile.am

@@ -54,6 +54,7 @@ leaky-dash			\
 leaky-polygon			\
 line-width			\
 line-width-scale		\
+line-width-zero			\
 linear-gradient			\
 linear-gradient-reflect		\
 long-lines			\

test/line-width-zero.c

@@ -0,0 +1,79 @@
+/*
+ * Copyright © 2007 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * Author: Carl Worth <cworth@cworth.org>
+ */
+
+#include "cairo-test.h"
+
+/* This is a test case for the following bug:
+ *
+ *	Crash in cairo_stroke_extents whe line width is 0 and line cap is ROUND
+ *	(_cairo_pen_find_active_cw_vertex_index)
+ *	https://bugs.freedesktop.org/show_bug.cgi?id=10231
+ */
+
+static cairo_test_draw_function_t draw;
+
+cairo_test_t test = {
+    "line-width-zero",
+    "Test all stroke operations and all cap,join styles with line width of zero",
+    0, 0,
+    draw
+};
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    double x1, y1, x2, y2;
+
+    cairo_move_to (cr, 0.0, 0.0);
+    cairo_line_to (cr, 100.0, 100.0);
+    cairo_set_line_width (cr, 0.0);
+
+    cairo_set_line_cap (cr, CAIRO_LINE_CAP_BUTT);
+    cairo_set_line_join (cr, CAIRO_LINE_JOIN_MITER);
+    cairo_stroke_extents (cr, &x1, &y1, &x2, &y2);
+    cairo_in_stroke (cr, 50, 50);
+    cairo_stroke_preserve (cr);
+
+    cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);
+    cairo_set_line_join (cr, CAIRO_LINE_JOIN_ROUND);
+    cairo_stroke_extents (cr, &x1, &y1, &x2, &y2);
+    cairo_in_stroke (cr, 50, 50);
+    cairo_stroke_preserve (cr);
+
+    cairo_set_line_cap (cr, CAIRO_LINE_CAP_SQUARE);
+    cairo_set_line_join (cr, CAIRO_LINE_JOIN_BEVEL);
+    cairo_stroke_extents (cr, &x1, &y1, &x2, &y2);
+    cairo_in_stroke (cr, 50, 50);
+    cairo_stroke (cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+int
+main (void)
+{
+    return cairo_test (&test);
+}