fix for android NDK r10e (#375)

src/complexity.cc

@@ -35,9 +35,9 @@ BigOFunc* FittingCurve(BigO complexity) {
     case oNCubed:
       return [](int n) -> double { return std::pow(n, 3); };
     case oLogN:
-      return [](int n) { return std::log2(n); };
+      return [](int n) { return log2(n); };
     case oNLogN:
-      return [](int n) { return n * std::log2(n); };
+      return [](int n) { return n * log2(n); };
     case o1:
     default:
       return [](int) { return 1.0; };

test/complexity_test.cc

@@ -141,7 +141,7 @@ BENCHMARK(BM_Complexity_O_N_log_N)
 BENCHMARK(BM_Complexity_O_N_log_N)
     ->RangeMultiplier(2)
     ->Range(1 << 10, 1 << 16)
-    ->Complexity([](int n) { return n * std::log2(n); });
+    ->Complexity([](int n) { return n * log2(n); });
 BENCHMARK(BM_Complexity_O_N_log_N)
     ->RangeMultiplier(2)
     ->Range(1 << 10, 1 << 16)