Add PCH support and 'CATCH_ENABLE_PCH' flag

tests/SelfTest/UsageTests/Compilation.tests.cpp

@@ -25,6 +25,16 @@ namespace bar {
     struct TypeList {};
 }
 
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-function"
+#endif
+#ifdef __GNUC__
+// Note that because -~GCC~-, this warning cannot be silenced temporarily, by pushing diagnostic stack...
+// Luckily it is firing in test files and thus can be silenced for the whole file, without losing much.
+#pragma GCC diagnostic ignored "-Wunused-function"
+#endif
+
 #ifdef __GNUC__
 #pragma GCC diagnostic ignored "-Wmissing-declarations"
 #endif
@@ -77,16 +87,6 @@ struct B : private A {
     bool operator==(int) const { return true; }
 };
 
-#ifdef __clang__
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wunused-function"
-#endif
-#ifdef __GNUC__
-// Note that because -~GCC~-, this warning cannot be silenced temporarily, by pushing diagnostic stack...
-// Luckily it is firing in test files and thus can be silenced for the whole file, without losing much.
-#pragma GCC diagnostic ignored "-Wunused-function"
-#endif
-
 B f();
 
 std::ostream g();

tests/SelfTest/UsageTests/ToStringOptional.tests.cpp

@@ -11,6 +11,8 @@
 
 #if defined(CATCH_CONFIG_CPP17_OPTIONAL)
 
+#include <optional>
+
 TEST_CASE( "std::optional<int> -> toString", "[toString][optional][approvals]" ) {
     using type = std::optional<int>;
     REQUIRE( "{ }" == ::Catch::Detail::stringify( type{} ) );