fix & suppress warnings of generated code

src/Base/Quantity.cpp

@@ -356,7 +356,15 @@ int QuantityLexer(void);
 
 #ifndef DOXYGEN_SHOULD_SKIP_THIS
 // Scanner, defined in QuantityParser.l
+#if defined(__clang__)
+# pragma clang diagnostic push
+# pragma clang diagnostic ignored "-Wsign-compare"
+# pragma clang diagnostic ignored "-Wunneeded-internal-declaration"
+#endif
 #include "QuantityLexer.c"
+#if defined(__clang__)
+# pragma clang diagnostic pop
+#endif
 #endif // DOXYGEN_SHOULD_SKIP_THIS
 }