Simple benchmarking framework

Benchmarking framework, loosely based on google's micro-benchmarking
library (https://github.com/google/benchmark)

Wny not use the Google Benchmark framework? Because adding Even More Dependencies
isn't worth it. If we get a dozen or three benchmarks and need nanosecond-accurate
timings of threaded code then switching to the full-blown Google Benchmark library
should be considered.

The benchmark framework is hard-coded to run each benchmark for one wall-clock second,
and then spits out .csv-format timing information to stdout. It is left as an
exercise for later (or maybe never) to add command-line arguments to specify which
benchmark(s) to run, how long to run them for, how to format results, etc etc etc.
Again, see the Google Benchmark framework for where that might end up.

See src/bench/MilliSleep.cpp for a sanity-test benchmark that just benchmarks
'sleep 100 milliseconds.'

To compile and run benchmarks:
  cd src; make bench

Sample output:

Benchmark,count,min,max,average
Sleep100ms,10,0.101854,0.105059,0.103881

1 files changed, 69 insertions, 0 deletions

diff --git a/src/bench/bench.h b/src/bench/bench.h
new file mode 100644
index 0000000000..fee9b8c38d
--- /dev/null
+++ b/src/bench/bench.h
@@ -0,0 +1,69 @@
+// Copyright (c) 2015 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#ifndef BITCOIN_BENCH_H
+#define BITCOIN_BENCH_H
+
+// Simple micro-benchmarking framework; API mostly matches a subset of the Google Benchmark
+// framework (see https://github.com/google/benchmark)
+// Wny not use the Google Benchmark framework? Because adding Yet Another Dependency
+// (that uses cmake as its build system and has lots of features we don't need) isn't
+// worth it.
+
+/*
+ * Usage:
+
+static void CODE_TO_TIME(benchmark::State& state)
+{
+    ... do any setup needed...
+    while (state.KeepRunning()) {
+       ... do stuff you want to time...
+    }
+    ... do any cleanup needed...
+}
+
+BENCHMARK(CODE_TO_TIME);
+
+ */
+
+
+#include <boost/function.hpp>
+#include <boost/preprocessor/cat.hpp>
+#include <boost/preprocessor/stringize.hpp>
+#include <map>
+#include <string>
+
+namespace benchmark {
+
+    class State {
+        std::string name;
+        double maxElapsed;
+        double beginTime;
+        double lastTime, minTime, maxTime;
+        int64_t count;
+    public:
+        State(std::string _name, double _maxElapsed) : name(_name), maxElapsed(_maxElapsed), count(0) {
+            minTime = std::numeric_limits<double>::max();
+            maxTime = std::numeric_limits<double>::min();
+        }
+        bool KeepRunning();
+    };
+
+    typedef boost::function<void(State&)> BenchFunction;
+
+    class BenchRunner
+    {
+        static std::map<std::string, BenchFunction> benchmarks;
+
+    public:
+        BenchRunner(std::string name, BenchFunction func);
+
+        static void RunAll(double elapsedTimeForOne=1.0);
+    };
+}
+
+// BENCHMARK(foo) expands to:  benchmark::BenchRunner bench_11foo("foo", foo);
+#define BENCHMARK(n) \
+    benchmark::BenchRunner BOOST_PP_CAT(bench_, BOOST_PP_CAT(__LINE__, n))(BOOST_PP_STRINGIZE(n), n);
+
+#endif // BITCOIN_BENCH_H