Add stringification for std::chrono::{duration,time_point}

Also hides std::chrono, std::pair and std::chrono::* behind
new configuration macros, CATCH_CONFIG_ENABLE_*_STRINGMAKER
to avoid dragging in <utility>, <tuple> and <chrono> in common
path, unless requested.

projects/SelfTest/ToStringChrono.cpp

@@ -0,0 +1,41 @@
+#define CATCH_CONFIG_ENABLE_CHRONO_STRINGMAKER
+#include "catch.hpp"
+
+#include <chrono>
+#include <cstdint>
+
+TEST_CASE("Stringifying std::chrono::duration helpers", "[toString][chrono]") {
+    // No literals because we still support c++11
+    auto hour = std::chrono::hours(1);
+    auto minute = std::chrono::minutes(1);
+    auto seconds = std::chrono::seconds(60);
+    auto micro = std::chrono::microseconds(1);
+    auto milli = std::chrono::milliseconds(1);
+    auto nano = std::chrono::nanoseconds(1);
+    REQUIRE(minute == seconds);
+    REQUIRE(hour != seconds);
+    REQUIRE(micro != milli);
+    REQUIRE(nano != micro);
+}
+
+TEST_CASE("Stringifying std::chrono::duration with weird ratios", "[toString][chrono]") {
+    std::chrono::duration<int64_t, std::ratio<30>> half_minute(1);
+    std::chrono::duration<int64_t, std::ratio<1, 1000000000000000>> femto_second(1);
+    REQUIRE(half_minute != femto_second);
+}
+
+TEST_CASE("Stringifying std::chrono::time_point<system_clock>", "[toString][chrono]") {
+    auto now = std::chrono::system_clock::now();
+    auto later = now + std::chrono::minutes(2);
+    REQUIRE(now != later);
+}
+
+TEST_CASE("Stringifying std::chrono::time_point<Clock>", "[toString][chrono]") {
+    auto now = std::chrono::high_resolution_clock::now();
+    auto later = now + std::chrono::minutes(2);
+    REQUIRE(now != later);
+
+    auto now2 = std::chrono::steady_clock::now();
+    auto later2 = now2 + std::chrono::minutes(2);
+    REQUIRE(now2 != later2);
+}