Add the FindCARES cmake module

cmake/Modules/FindCARES.cmake

+# - Find c-ares
+# Find the c-ares library, and more particularly the stringprep header.
+#
+# This module defines the following variables:
+#   CARES_FOUND  -  True if library and include directory are found
+# If set to TRUE, the following are also defined:
+#   CARES_INCLUDE_DIRS  -  The directory where to find the header file
+#   CARES_LIBRARIES  -  Where to find the library file
+#
+# For conveniance, these variables are also set. They have the same values
+# than the variables above.  The user can thus choose his/her prefered way
+# to write them.
+#   CARES_INCLUDE_DIR
+#   CARES_LIBRARY
+#
+# This file is in the public domain
+
+if(NOT CARES_FOUND)
+  find_path(CARES_INCLUDE_DIRS NAMES ares.h
+    DOC "The c-ares include directory")
+
+  find_library(CARES_LIBRARIES NAMES cares
+    DOC "The c-ares library")
+
+  # Use some standard module to handle the QUIETLY and REQUIRED arguments, and
+  # set CARES_FOUND to TRUE if these two variables are set.
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(CARES REQUIRED_VARS CARES_LIBRARIES CARES_INCLUDE_DIRS)
+
+  # Compatibility for all the ways of writing these variables
+  if(CARES_FOUND)
+    set(CARES_INCLUDE_DIR ${CARES_INCLUDE_DIRS})
+    set(CARES_LIBRARY ${CARES_LIBRARIES})
+  endif()
+endif()
+
+mark_as_advanced(CARES_INCLUDE_DIRS CARES_LIBRARIES)