Use pragma to suppress -Wpedantic for __int128 typedef

__extension__ doesn't work in using declarations with GCC.
Use #pragma GCC diagnostic push/pop instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Dendi Suhubdy

src/crypto/field25519.cpp

@@ -4,7 +4,10 @@
 namespace tor::crypto {
 
 using u64 = uint64_t;
-using u128 = __extension__ unsigned __int128;
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wpedantic"
+using u128 = unsigned __int128;
+#pragma GCC diagnostic pop
 
 static constexpr u64 MASK51 = FieldElement::MASK51;
 

src/crypto/secretbox.cpp

@@ -231,7 +231,10 @@ void poly1305(
     std::span<const uint8_t> message,
     std::span<const uint8_t, 32> key) {
 
-    using u128 = __extension__ unsigned __int128;
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wpedantic"
+    using u128 = unsigned __int128;
+#pragma GCC diagnostic pop
 
     // Clamp r (first 16 bytes of key)
     uint32_t r0 = load32_le(key.data())      & 0x0fffffff;