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++/metrics.h

@@ -0,0 +1,92 @@
+// Copyright 2011 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef NINJA_METRICS_H_
+#define NINJA_METRICS_H_
+
+#include <string>
+#include <vector>
+using namespace std;
+
+#include "util.h"  // For int64_t.
+
+/// The Metrics module is used for the debug mode that dumps timing stats of
+/// various actions.  To use, see METRIC_RECORD below.
+
+/// A single metrics we're tracking, like "depfile load time".
+struct Metric {
+  string name;
+  /// Number of times we've hit the code path.
+  int count;
+  /// Total time (in micros) we've spent on the code path.
+  int64_t sum;
+};
+
+
+/// A scoped object for recording a metric across the body of a function.
+/// Used by the METRIC_RECORD macro.
+struct ScopedMetric {
+  explicit ScopedMetric(Metric* metric);
+  ~ScopedMetric();
+
+private:
+  Metric* metric_;
+  /// Timestamp when the measurement started.
+  /// Value is platform-dependent.
+  int64_t start_;
+};
+
+/// The singleton that stores metrics and prints the report.
+struct Metrics {
+  Metric* NewMetric(const string& name);
+
+  /// Print a summary report to stdout.
+  void Report();
+
+private:
+  vector<Metric*> metrics_;
+};
+
+/// Get the current time as relative to some epoch.
+/// Epoch varies between platforms; only useful for measuring elapsed time.
+int64_t GetTimeMillis();
+
+/// A simple stopwatch which returns the time
+/// in seconds since Restart() was called.
+struct Stopwatch {
+ public:
+  Stopwatch() : started_(0) {}
+
+  /// Seconds since Restart() call.
+  double Elapsed() const {
+    return 1e-6 * static_cast<double>(Now() - started_);
+  }
+
+  void Restart() { started_ = Now(); }
+
+ private:
+  uint64_t started_;
+  uint64_t Now() const;
+};
+
+/// The primary interface to metrics.  Use METRIC_RECORD("foobar") at the top
+/// of a function to get timing stats recorded for each call of the function.
+#define METRIC_RECORD(name)                                             \
+  static Metric* metrics_h_metric =                                     \
+      g_metrics ? g_metrics->NewMetric(name) : NULL;                    \
+  ScopedMetric metrics_h_scoped(metrics_h_metric);
+
+extern Metrics* g_metrics;
+
+#endif // NINJA_METRICS_H_