Use ENABLE_GCC_WARNING and DISABLE_GCC_WARNING in tortls.c

Previously we'd done this ad hoc.

src/common/tortls.c

@@ -24,17 +24,12 @@
   #include <ws2tcpip.h>
 #endif
 
-#ifdef __GNUC__
-#define GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
-#endif
+#include "compat.h"
 
-#if __GNUC__ && GCC_VERSION >= 402
-#if GCC_VERSION >= 406
-#pragma GCC diagnostic push
-#endif
+#if GCC_VERSION >= 402
 /* Some versions of OpenSSL declare SSL_get_selected_srtp_profile twice in
  * srtp.h. Suppress the GCC warning so we can build with -Wredundant-decl. */
-#pragma GCC diagnostic ignored "-Wredundant-decls"
+DISABLE_GCC_WARNING(redundant-decls)
 #endif
 
 #include <openssl/opensslv.h>
@@ -53,12 +48,8 @@
 #include <openssl/bn.h>
 #include <openssl/rsa.h>
 
-#if __GNUC__ && GCC_VERSION >= 402
-#if GCC_VERSION >= 406
-#pragma GCC diagnostic pop
-#else
-#pragma GCC diagnostic warning "-Wredundant-decls"
-#endif
+#if GCC_VERSION >= 402
+ENABLE_GCC_WARNING(redundant-decls)
 #endif
 
 #ifdef USE_BUFFEREVENTS