[MINOR] checks: add support for LDAPv3 health checks

This patch provides a new "option ldap-check" statement to enable
server health checks based on LDAPv3 bind requests.
(cherry picked from commit b76b44c6fed8a7ba6f0f565dd72a9cb77aaeca7c)
diff --git a/include/common/defaults.h b/include/common/defaults.h
index 845319d..84ab3d4 100644
--- a/include/common/defaults.h
+++ b/include/common/defaults.h
@@ -118,6 +118,7 @@
 #define DEF_RISETIME    2
 #define DEF_CHECK_REQ   "OPTIONS / HTTP/1.0\r\n"
 #define DEF_SMTP_CHECK_REQ   "HELO localhost\r\n"
+#define DEF_LDAP_CHECK_REQ   "\x30\x0c\x02\x01\x01\x60\x07\x02\x01\x03\x04\x00\x80\x00"
 
 #define DEF_HANA_ONERR		HANA_ONERR_FAILCHK
 #define DEF_HANA_ERRLIMIT	10