Fix FTBFS on ancient Heimdal versions

diff --git a/src/Makefile.am b/src/Makefile.am
index 5d5b855..6a64b3d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -7,6 +7,7 @@
 include_HEADERS = libtdeldap.h ldappasswddlg.h
 
 libtdeldap_la_SOURCES = libtdeldap.cpp ldaplogindlgbase.ui ldaplogindlg.cpp ldappasswddlg.cpp
+libtdeldap_la_CPPFLAGS = -fpermissive
 libtdeldap_la_LIBADD = -ltdeio $(LIB_TDEUI) -lldap $(LIB_QT) $(LIB_TDECORE) -ltdesu -llber -lkadm5clnt -lkadm5srv
 libtdeldap_la_LDFLAGS = -version-info $(lt_current):$(lt_revision):$(lt_age) -no-undefined \
 	$(all_libraries)
diff --git a/src/libtdeldap.cpp b/src/libtdeldap.cpp
index bc6890b..0549759 100644
--- a/src/libtdeldap.cpp
+++ b/src/libtdeldap.cpp
@@ -51,6 +51,8 @@
 #include <sys/un.h>
 
 extern "C" {
+	#include <krb5.h>
+	#include <krb5_asn1.h>
 	#include <hdb.h>
 	#include <hdb_asn1.h>
 	#include <kadm5/admin.h>
@@ -1089,6 +1091,7 @@
 		}
 		TQByteArray acl_asn1_data;
 		if (pkinit_acl_subject != "") {
+#if HDB_INTERFACE_VERSION > 4
 			krb5_error_code krb5_ret;
 			HDB_extension extended_attributes;
 			memset(&extended_attributes, 0, sizeof(extended_attributes));
@@ -1110,6 +1113,7 @@
 			}
 			free(pkinit_acl->val);
 			free(asn1_encoding_buf);
+#endif
 		}
 
 		// Assemble the LDAPMod structure