ENH: add optional support for c-ares

CMake/FindCARES.cmake

@@ -0,0 +1,42 @@
+# - Find c-ares
+# Find the c-ares includes and library
+# This module defines
+#  CARES_INCLUDE_DIR, where to find ares.h, etc.
+#  CARES_LIBRARIES, the libraries needed to use c-ares.
+#  CARES_FOUND, If false, do not try to use c-ares.
+# also defined, but not for general use are
+# CARES_LIBRARY, where to find the c-ares library.
+	
+FIND_PATH(CARES_INCLUDE_DIR ares.h
+  /usr/local/include
+  /usr/include
+  )
+ 	
+SET(CARES_NAMES ${CARES_NAMES} cares)
+FIND_LIBRARY(CARES_LIBRARY
+  NAMES ${CARES_NAMES}
+  PATHS /usr/lib /usr/local/lib
+  )
+
+IF (CARES_LIBRARY AND CARES_INCLUDE_DIR)
+  SET(CARES_LIBRARIES ${CARES_LIBRARY})
+  SET(CARES_FOUND "YES")
+ELSE (CARES_LIBRARY AND CARES_INCLUDE_DIR)
+  SET(CARES_FOUND "NO")
+ENDIF (CARES_LIBRARY AND CARES_INCLUDE_DIR)
+
+
+IF (CARES_FOUND)
+  IF (NOT CARES_FIND_QUIETLY)
+    MESSAGE(STATUS "Found c-ares: ${CARES_LIBRARIES}")
+  ENDIF (NOT CARES_FIND_QUIETLY)
+ELSE (CARES_FOUND)
+  IF (CARES_FIND_REQUIRED)
+    MESSAGE(FATAL_ERROR "Could not find c-ares library")
+  ENDIF (CARES_FIND_REQUIRED)
+ENDIF (CARES_FOUND)
+
+MARK_AS_ADVANCED(
+  CARES_LIBRARY
+  CARES_INCLUDE_DIR
+  )