Create a top-level "third_party" directory

This directory now contains third_party software that is vendored into
the Servo source tree. The idea is that it would eventually hold
webrender and other crates from mozilla-central as well with a standard
patch management approach for each.

third_party/ply/example/yply/yply.py

@@ -0,0 +1,51 @@
+#!/usr/local/bin/python
+# yply.py
+#
+# Author: David Beazley (dave@dabeaz.com)
+# Date  : October 2, 2006
+#
+# Converts a UNIX-yacc specification file into a PLY-compatible
+# specification.   To use, simply do this:
+#
+#   % python yply.py [-nocode] inputfile.y >myparser.py
+#
+# The output of this program is Python code. In the output,
+# any C code in the original file is included, but is commented.
+# If you use the -nocode option, then all of the C code in the
+# original file is discarded.
+#
+# Disclaimer:  This just an example I threw together in an afternoon.
+# It might have some bugs.  However, it worked when I tried it on
+# a yacc-specified C++ parser containing 442 rules and 855 parsing
+# states.
+#
+
+import sys
+sys.path.insert(0, "../..")
+
+import ylex
+import yparse
+
+from ply import *
+
+if len(sys.argv) == 1:
+    print("usage : yply.py [-nocode] inputfile")
+    raise SystemExit
+
+if len(sys.argv) == 3:
+    if sys.argv[1] == '-nocode':
+        yparse.emit_code = 0
+    else:
+        print("Unknown option '%s'" % sys.argv[1])
+        raise SystemExit
+    filename = sys.argv[2]
+else:
+    filename = sys.argv[1]
+
+yacc.parse(open(filename).read())
+
+print("""
+if __name__ == '__main__':
+    from ply import *
+    yacc.yacc()
+""")