Fix libxml2 CFLAGS output

configure.ac

@@ -899,7 +899,7 @@ AC_MSG_NOTICE([summary of build options:
       Failmalloc:     ${enable_failmalloc}
     Libs:
       OpenSSL:        ${have_openssl} (CFLAGS='${OPENSSL_CFLAGS}' LIBS='${OPENSSL_LIBS}')
-      Libxml2:        ${have_libxml2} (CFLAGS='${LIBXML2_CPPFLAGS}' LIBS='${LIBXML2_LIBS}')
+      Libxml2:        ${have_libxml2} (CFLAGS='${LIBXML2_CFLAGS}' LIBS='${LIBXML2_LIBS}')
       Libev:          ${have_libev} (CFLAGS='${LIBEV_CFLAGS}' LIBS='${LIBEV_LIBS}')
       Libc-ares       ${have_libcares} (CFLAGS='${LIBCARES_CFLAGS}' LIBS='${LIBCARES_LIBS}')
       Libevent(SSL):  ${have_libevent_openssl} (CFLAGS='${LIBEVENT_OPENSSL_CFLAGS}' LIBS='${LIBEVENT_OPENSSL_LIBS}')