patch 8.1.1927: code for dealing with script files is spread out

Problem:    Code for dealing with script files is spread out.
Solution:   Move the code to scriptfile.c. (Yegappan Lakshmanan, closes #4861)
diff --git a/src/Make_morph.mak b/src/Make_morph.mak
index c41e853..08111aa 100644
--- a/src/Make_morph.mak
+++ b/src/Make_morph.mak
@@ -77,6 +77,7 @@
 	profiler.c						\
 	quickfix.c						\
 	regexp.c						\
+	scriptfile.c						\
 	screen.c						\
 	search.c						\
 	session.c						\