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/hedit/hedit.py

@@ -0,0 +1,48 @@
+# -----------------------------------------------------------------------------
+# hedit.py
+#
+# Paring of Fortran H Edit descriptions (Contributed by Pearu Peterson)
+#
+# These tokens can't be easily tokenized because they are of the following
+# form:
+#
+#   nHc1...cn
+#
+# where n is a positive integer and c1 ... cn are characters.
+#
+# This example shows how to modify the state of the lexer to parse
+# such tokens
+# -----------------------------------------------------------------------------
+
+import sys
+sys.path.insert(0, "../..")
+
+
+tokens = (
+    'H_EDIT_DESCRIPTOR',
+)
+
+# Tokens
+t_ignore = " \t\n"
+
+
+def t_H_EDIT_DESCRIPTOR(t):
+    r"\d+H.*"                     # This grabs all of the remaining text
+    i = t.value.index('H')
+    n = eval(t.value[:i])
+
+    # Adjust the tokenizing position
+    t.lexer.lexpos -= len(t.value) - (i + 1 + n)
+
+    t.value = t.value[i + 1:i + 1 + n]
+    return t
+
+
+def t_error(t):
+    print("Illegal character '%s'" % t.value[0])
+    t.lexer.skip(1)
+
+# Build the lexer
+import ply.lex as lex
+lex.lex()
+lex.runmain()