mingw: update TLS option flags

Include the constants for `WINHTTP_FLAG_SECURE_PROTOCOL_TLS1_1` and
`WINHTTP_FLAG_SECURE_PROTOCOL_TLS1_2` so that they can be used by mingw.

This updates both the `deps/winhttp` framework (for classic mingw) and
adds the defines for mingw64, which does not use that framework.

deps/winhttp/winhttp.h

@@ -440,6 +440,8 @@ typedef int INTERNET_SCHEME, *LPINTERNET_SCHEME;
 #define WINHTTP_FLAG_SECURE_PROTOCOL_SSL2    0x00000008
 #define WINHTTP_FLAG_SECURE_PROTOCOL_SSL3    0x00000020
 #define WINHTTP_FLAG_SECURE_PROTOCOL_TLS1    0x00000080
+#define WINHTTP_FLAG_SECURE_PROTOCOL_TLS1_1  0x00000200
+#define WINHTTP_FLAG_SECURE_PROTOCOL_TLS1_2  0x00000800
 #define WINHTTP_FLAG_SECURE_PROTOCOL_ALL     (WINHTTP_FLAG_SECURE_PROTOCOL_SSL2 | WINHTTP_FLAG_SECURE_PROTOCOL_SSL3 | WINHTTP_FLAG_SECURE_PROTOCOL_TLS1)
 
 #define WINHTTP_AUTH_SCHEME_BASIC      0x00000001

src/transports/winhttp.c

@@ -52,6 +52,11 @@ static const int no_check_cert_flags = SECURITY_FLAG_IGNORE_CERT_CN_INVALID |
 	SECURITY_FLAG_IGNORE_CERT_DATE_INVALID |
 	SECURITY_FLAG_IGNORE_UNKNOWN_CA;
 
+#if defined(__MINGW64_VERSION_MAJOR)
+# define WINHTTP_FLAG_SECURE_PROTOCOL_TLS1_1 0x00000200
+# define WINHTTP_FLAG_SECURE_PROTOCOL_TLS1_2 0x00000800
+#endif
+
 #if defined(__MINGW32__)
 static const CLSID CLSID_InternetSecurityManager_mingw =
 	{ 0x7B8A2D94, 0x0AC9, 0x11D1,