Use udns instead of c-ares

fix #3226

louloulibs/cmake/Modules/FindUDNS.cmake

@@ -0,0 +1,37 @@
+# - Find udns
+# Find the udns library
+#
+# This module defines the following variables:
+#   UDNS_FOUND  -  True if library and include directory are found
+# If set to TRUE, the following are also defined:
+#   UDNS_INCLUDE_DIRS  -  The directory where to find the header file
+#   UDNS_LIBRARIES  -  Where to find the library file
+#
+# For conveniance, these variables are also set. They have the same values
+# as the variables above.  The user can thus choose his/her prefered way
+# to write them.
+#   UDNS_INCLUDE_DIR
+#   UDNS_LIBRARY
+#
+# This file is in the public domain
+
+if(NOT UDNS_FOUND)
+  find_path(UDNS_INCLUDE_DIRS NAMES udns.h
+    DOC "The udns include directory")
+
+  find_library(UDNS_LIBRARIES NAMES udns
+    DOC "The udns library")
+
+  # Use some standard module to handle the QUIETLY and REQUIRED arguments, and
+  # set UDNS_FOUND to TRUE if these two variables are set.
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(UDNS REQUIRED_VARS UDNS_LIBRARIES UDNS_INCLUDE_DIRS)
+
+  # Compatibility for all the ways of writing these variables
+  if(UDNS_FOUND)
+    set(UDNS_INCLUDE_DIR ${UDNS_INCLUDE_DIRS})
+    set(UDNS_LIBRARY ${UDNS_LIBRARIES})
+  endif()
+endif()
+
+mark_as_advanced(UDNS_INCLUDE_DIRS UDNS_LIBRARIES)