Added m4/libcares.m4

m4/libcares.m4

@@ -0,0 +1,33 @@
+AC_DEFUN([AM_PATH_LIBCARES],
+[
+AC_ARG_WITH([libcares-prefix],
+            [  --with-libcares-prefix=PREFIX  Prefix where libcares installed (optional)],
+            [libcares_prefix=$withval],
+            [libcares_prefix=""])
+
+if test "x$libcares_prefix" = "x"; then
+  libcares_prefix="/usr"
+fi
+
+libcares_prefix_lib=$libcares_prefix/lib
+libcares_prefix_include=$libcares_prefix/include
+
+LIBS_save=$LIBS
+CPPFLAGS_save=$CPPFLAGS
+
+LIBS="-L$libcares_prefix_lib $LIBS"
+CPPFLAGS="-I$libcares_prefix_include $CPPFLAGS"
+
+AC_CHECK_LIB([cares], [ares_init], [have_libcares=yes])
+if test "x$have_libcares" = "xyes"; then
+    AC_DEFINE([HAVE_LIBCARES], [1], [Define to 1 if you have libcares.])
+    LIBCARES_LIBS="-L$libcares_prefix_lib -lcares"
+    LIBCARES_CPPFLAGS="-I$libcares_prefix_include"
+    AC_SUBST(LIBCARES_LIBS)
+    AC_SUBST(LIBCARES_CPPFLAGS)
+fi
+
+LIBS=$LIBS_save
+CPPFLAGS=$CPPFLAGS_save
+
+])