Add variadic CAPTURE tests

This makes sure that CAPTURE works when called with variadic arguments,
and also works that way when disabled.

The underlying fix to #2316 is not applicable (CAPTURE is already
variadic when disabled).

This is a port of 5e94498ed0 to the
devel branch.

tests/ExtraTests/X01-PrefixedMacros.cpp

@@ -66,6 +66,7 @@ CATCH_TEST_CASE("PrefixedMacros") {
     CATCH_SECTION("some section") {
         int i = 1;
         CATCH_CAPTURE( i );
+        CATCH_CAPTURE( i, i + 1 );
         CATCH_DYNAMIC_SECTION("Dynamic section: " << i) {
             CATCH_FAIL_CHECK( "failure" );
         }

tests/ExtraTests/X02-DisabledMacros.cpp

@@ -52,6 +52,9 @@ TEST_CASE( "Disabled Macros" ) {
     STATIC_CHECK( 0 == 1 );
     STATIC_REQUIRE( !true );
 
+    CAPTURE( 1 );
+    CAPTURE( 1, "captured" );
+
     REQUIRE_THAT( 1,
                   Catch::Matchers::Predicate( []( int ) { return false; } ) );
     BENCHMARK( "Disabled benchmark" ) { REQUIRE( 1 == 2 ); };