patch 7.4.1479
Problem:    No testfor ":loadplugin".
Solution:   Add a test.  Fix how option is being set.
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 8901b15..4c3c616 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -178,6 +178,7 @@
 	    test_increment.res \
 	    test_json.res \
 	    test_langmap.res \
+	    test_loadplugin.res \
 	    test_perl.res \
 	    test_quickfix.res \
 	    test_syntax.res \