Drop usage of non-Standard stdext (#1339)

* Drop usage of non-Standard stdext.

* Instead add an upper limit to the MSVC version.

Author: StephanTLavavej

integer.cpp

@@ -3056,7 +3056,7 @@ Integer::Integer(const byte *encodedInteger, size_t byteCount, Signedness s, Byt
 	else
 	{
 		SecByteBlock block(byteCount);
-#if (CRYPTOPP_MSC_VERSION >= 1500)
+#if (CRYPTOPP_MSC_VERSION >= 1500) && (CRYPTOPP_MSC_VERSION < 1938)
 		std::reverse_copy(encodedInteger, encodedInteger+byteCount,
 			stdext::make_checked_array_iterator(block.begin(), block.size()));
 #else

zdeflate.cpp

@@ -412,13 +412,8 @@ unsigned int Deflator::LongestMatch(unsigned int &bestMatch) const
 		if (scan[bestLength-1] == match[bestLength-1] && scan[bestLength] == match[bestLength] && scan[0] == match[0] && scan[1] == match[1])
 		{
 			CRYPTOPP_ASSERT(scan[2] == match[2]);
-			unsigned int len = (unsigned int)(
-#if defined(_STDEXT_BEGIN) && !(defined(CRYPTOPP_MSC_VERSION) && (CRYPTOPP_MSC_VERSION < 1400 || CRYPTOPP_MSC_VERSION >= 1600)) && !defined(_STLPORT_VERSION)
-				stdext::unchecked_mismatch
-#else
-				std::mismatch
-#endif
-#if CRYPTOPP_MSC_VERSION >= 1600
+			unsigned int len = (unsigned int)(std::mismatch
+#if (CRYPTOPP_MSC_VERSION >= 1600) && (CRYPTOPP_MSC_VERSION < 1938)
 				(stdext::make_unchecked_array_iterator(scan)+3, stdext::make_unchecked_array_iterator(scanEnd), stdext::make_unchecked_array_iterator(match)+3).first - stdext::make_unchecked_array_iterator(scan));
 #else
 				(scan+3, scanEnd, match+3).first - scan);