[librsvg] Add test case for issue #336

[Paolo Borelli <pborelli src gnome org>]

commit 0f5480cefe738cfaf50dc122c0aaf3234c962161
Author: Paolo Borelli <pborelli gnome org>
Date:   Mon Nov 11 14:32:57 2019 +0100

    Add test case for issue #336
    
    This is now fixed with the switch from croco to cssparser

 tests/fixtures/infinite-loop/336-invalid-css.svg | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/tests/fixtures/infinite-loop/336-invalid-css.svg 
b/tests/fixtures/infinite-loop/336-invalid-css.svg
new file mode 100644
index 00000000..7486f96d
--- /dev/null
+++ b/tests/fixtures/infinite-loop/336-invalid-css.svg
@@ -0,0 +1,7 @@
+<?xml version="1.0" ?>
+<svg height="100" width="100" xmlns="http://www.w3.org/2000/svg";>
+  <style>
+.c {
+   a: b
+  </style>
+</svg>