Redo HTTP cookie parsing (#510)

* Redo HTTP cookie parsing using strptime

* Make String(utf8Slice:from:) less ugly

* Adjust cookie component parsing to better match RFC-6562

Sources/CAsyncHTTPClient/CAsyncHTTPClient.c

@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the AsyncHTTPClient open source project
+//
+// Copyright (c) 2018-2021 Apple Inc. and the AsyncHTTPClient project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of AsyncHTTPClient project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+#if __APPLE__
+    #include <xlocale.h>
+#elif __linux__
+    #define _GNU_SOURCE
+    #include <locale.h>
+#endif
+
+#include <stdbool.h>
+#include <time.h>
+
+bool swiftahc_cshims_strptime(const char * string, const char * format, struct tm * result) {
+    const char * firstNonProcessed = strptime(string, format, result);
+    if (firstNonProcessed) {
+        return *firstNonProcessed == 0;
+    }
+    return false;
+}
+
+bool swiftahc_cshims_strptime_l(const char * string, const char * format, struct tm * result, void * locale) {
+    // The pointer cast is fine as long we make sure it really points to a locale_t.
+    const char * firstNonProcessed = strptime_l(string, format, result, (locale_t)locale);
+    if (firstNonProcessed) {
+        return *firstNonProcessed == 0;
+    }
+    return false;
+}