Fixed tests so they build on android.

- Added missing header to test/benchmark_test.cc
- Changed std::stoul to std::atol in test/filter_test.cc because of a
  limitation in the android-ndk (http://stackoverflow.com/questions/17950814/how-to-use-stdstoul-and-stdstoull-in-android)

test/benchmark_test.cc

@@ -13,6 +13,7 @@
 #include <sstream>
 #include <string>
 #include <vector>
+#include <cstdlib>
 
 #if defined(__GNUC__)
 # define BENCHMARK_NOINLINE __attribute__((noinline))

test/filter_test.cc

@@ -3,6 +3,7 @@
 #include <cassert>
 #include <cmath>
 #include <cstdint>
+#include <cstdlib>
 
 #include <iostream>
 #include <limits>
@@ -75,7 +76,7 @@ int main(int argc, char* argv[]) {
 
   // Make sure we ran all of the tests
   const size_t count = test_reporter.GetCount();
-  const size_t expected = (argc == 2) ? std::stoul(argv[1]) : count;
+  const size_t expected = (argc == 2) ? std::atol(argv[1]) : count;
   if (count != expected) {
     std::cerr << "ERROR: Expected " << expected << " tests to be ran but only "
               << count << " completed" << std::endl;