Fix tutorials/http/http-server build with windows gcc

src/tls_rsa.c

@@ -63,7 +63,7 @@ typedef uint16_t comp;            /**< A single precision component. */
 typedef uint32_t long_comp;       /**< A double precision component. */
 typedef int32_t slong_comp;       /**< A signed double precision component. */
 #else                        /* regular 32 bit */
-#ifdef WIN32
+#ifdef _MSC_VER
 #define COMP_RADIX 4294967296i64
 #define COMP_MAX 0xFFFFFFFFFFFFFFFFui64
 #else