patch 8.1.1195: Vim script debugger functionality needs cleanup

Problem:    Vim script debugger functionality needs cleanup.
Solution:   Move debugger code to a separate file.  Add more tests. (Yegappan
            Lakshmanan, closes #4285)
diff --git a/src/Make_morph.mak b/src/Make_morph.mak
index b224c67..65cf844 100644
--- a/src/Make_morph.mak
+++ b/src/Make_morph.mak
@@ -31,6 +31,7 @@
 	charset.c						\
 	crypt.c							\
 	crypt_zip.c						\
+	debugger.c						\
 	dict.c							\
 	diff.c							\
 	digraph.c						\