patch 8.1.0729: there is a SourcePre autocommand event but not a SourcePost

Problem:    There is a SourcePre autocommand event but not a SourcePost.
Solution:   Add the SourcePost autocommand event. (closes #3739)
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 8db2995..8d83516 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -222,6 +222,7 @@
 	test_signs \
 	test_smartindent \
 	test_sort \
+	test_source \
 	test_source_utf8 \
 	test_spell \
 	test_startup \
@@ -376,6 +377,7 @@
 	test_shortpathname.res \
 	test_signs.res \
 	test_smartindent.res \
+	test_source.res \
 	test_spell.res \
 	test_startup.res \
 	test_stat.res \