url: rename function due to name-clash in Watt-32

Since the commit 764c958c52, there was a new function called
resolve_ip(). This clashes with an internal function in Watt-32.

Closes #9585

lib/curl_setup.h

@@ -519,6 +519,9 @@
 #    ifdef byte
 #      undef byte
 #    endif
+#    ifdef resolve_ip
+#      undef resolve_ip
+#    endif
 
 #  endif /* MSDOS */