Exclude third-party code from Linguist stats

Author: quark17

.gitattributes

@@ -0,0 +1,9 @@
+# Tell Linguist not to include the following code
+# in statistics about this repo
+#
+src/Parsec/* linguist-vendored
+src/cudd/v2.5.0/src/* linguist-vendored
+src/stp/src/* linguist-vendored
+src/tcltk/tcltk8.5.4/* linguist-vendored
+src/tcltk/itcl3.4/* linguist-vendored
+src/tcltk/itk3.4/* linguist-vendored