sysutils/adtool: fix build on recent current

svn path=/head/; revision=546373

sysutils/adtool/files/patch-src_lib_active__directory.h

@@ -0,0 +1,19 @@
+--- src/lib/active_directory.h.orig	2020-08-27 17:21:27 UTC
++++ src/lib/active_directory.h
+@@ -28,11 +28,11 @@ searchbase ou=users,dc=example,dc=com
+ | if there is a problem reading the config file, or
+ |	AD_SERVER_CONNECT_FAILURE if a connection can't be made.
+ */
+-char *system_config_file;
+-char *uri;
+-char *binddn;
+-char *bindpw;
+-char *search_base;
++extern char *system_config_file;
++extern char *uri;
++extern char *binddn;
++extern char *bindpw;
++extern char *search_base;
+ 
+ /* ad_get_error() returns a pointer to a string containing an
+ | explanation of the last error that occured.