curl: Disable warnings to avoid changing 3rd party code

Tell MSVC to use its lowest warning level inside curl sources.

Utilities/cmcurl/lib/curl_setup.h

@@ -80,6 +80,10 @@
 
 #endif /* HAVE_CONFIG_H */
 
+#if defined(_MSC_VER)
+# pragma warning(push,1)
+#endif
+
 /* ================================================================ */
 /* Definition of preprocessor macros/symbols which modify compiler  */
 /* behavior or generated code characteristics must be done here,   */