Add test for new libuv callback styles.

This fixes a build warning on Mac.

CMakeLists.txt

@@ -794,6 +794,12 @@ endif ()
 if (USE_LIBUV)
   find_package(Libuv)
   if (Libuv_FOUND)
+    # Check for new-style callbacks.
+    try_compile(HAVE_NEW_UV_TIMER_CB
+      ${CMAKE_CURRENT_BINARY_DIR}
+      ${CMAKE_CURRENT_SOURCE_DIR}/cmake/tests/test_uv_cb.c
+    )
+
     # Copy module header to getdns include dir.
     file(COPY src/getdns/getdns_ext_libuv.h DESTINATION getdns)
 

cmake/include/cmakeconfig.h.in

@@ -207,6 +207,8 @@
 
 #cmakedefine USE_OSX_TCP_FASTOPEN	1
 
+#cmakedefine HAVE_NEW_UV_TIMER_CB	1
+
 #cmakedefine HAVE_TARGET_ENDIANNESS
 #cmakedefine TARGET_IS_BIG_ENDIAN
 

cmake/tests/test_uv_cb.c

@@ -0,0 +1,12 @@
+#include <uv.h>
+
+void test_cb(uv_timer_t *handle)
+{
+    (void) handle;
+}
+
+int main(int ac, char *av[])
+{
+    uv_timer_cb cb = test_cb;
+    (*cb)(0);
+}