Add a few samples of misclassified C++ headers

Several people mentioned in #467 that they were seeing their C++ projects
erroneously showing up as containing Objective C.

I've added a file from each of the problematic repositories:

  - https://github.com/mp13on11/dwarf_mine
  - https://github.com/miguelishawt/anax
  - https://github.com/mholt/cppcsv
  - https://github.com/coder543/libcanister

They all seem to be triggering on different aspects, since adding one sample
wasn't sufficient to correctly classify the others.

The discussion in #467 makes me think that perhaps Linuist might need to take
the rest of the repository into account when classifying ambiguous files.

samples/C++/Field.h

@@ -0,0 +1,32 @@
+/*****************************************************************************
+* Dwarf Mine - The 13-11 Benchmark
+*
+* Copyright (c) 2013 Bünger, Thomas; Kieschnick, Christian; Kusber,
+* Michael; Lohse, Henning; Wuttke, Nikolai; Xylander, Oliver; Yao, Gary;
+* Zimmermann, Florian
+*
+* Permission is hereby granted, free of charge, to any person obtaining
+* a copy of this software and associated documentation files (the
+* "Software"), to deal in the Software without restriction, including
+* without limitation the rights to use, copy, modify, merge, publish,
+* distribute, sublicense, and/or sell copies of the Software, and to
+* permit persons to whom the Software is furnished to do so, subject to
+* the following conditions:
+*
+* The above copyright notice and this permission notice shall be
+* included in all copies or substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*****************************************************************************/
+
+#pragma once
+
+enum Field { Free, Black, White, Illegal };
+
+typedef Field Player;