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/BASIC/basiclex.py

@@ -0,0 +1,61 @@
+# An implementation of Dartmouth BASIC (1964)
+
+from ply import *
+
+keywords = (
+    'LET', 'READ', 'DATA', 'PRINT', 'GOTO', 'IF', 'THEN', 'FOR', 'NEXT', 'TO', 'STEP',
+    'END', 'STOP', 'DEF', 'GOSUB', 'DIM', 'REM', 'RETURN', 'RUN', 'LIST', 'NEW',
+)
+
+tokens = keywords + (
+    'EQUALS', 'PLUS', 'MINUS', 'TIMES', 'DIVIDE', 'POWER',
+    'LPAREN', 'RPAREN', 'LT', 'LE', 'GT', 'GE', 'NE',
+    'COMMA', 'SEMI', 'INTEGER', 'FLOAT', 'STRING',
+    'ID', 'NEWLINE'
+)
+
+t_ignore = ' \t'
+
+
+def t_REM(t):
+    r'REM .*'
+    return t
+
+
+def t_ID(t):
+    r'[A-Z][A-Z0-9]*'
+    if t.value in keywords:
+        t.type = t.value
+    return t
+
+t_EQUALS = r'='
+t_PLUS = r'\+'
+t_MINUS = r'-'
+t_TIMES = r'\*'
+t_POWER = r'\^'
+t_DIVIDE = r'/'
+t_LPAREN = r'\('
+t_RPAREN = r'\)'
+t_LT = r'<'
+t_LE = r'<='
+t_GT = r'>'
+t_GE = r'>='
+t_NE = r'<>'
+t_COMMA = r'\,'
+t_SEMI = r';'
+t_INTEGER = r'\d+'
+t_FLOAT = r'((\d*\.\d+)(E[\+-]?\d+)?|([1-9]\d*E[\+-]?\d+))'
+t_STRING = r'\".*?\"'
+
+
+def t_NEWLINE(t):
+    r'\n'
+    t.lexer.lineno += 1
+    return t
+
+
+def t_error(t):
+    print("Illegal character %s" % t.value[0])
+    t.lexer.skip(1)
+
+lex.lex(debug=0)