patch 8.1.2001: some source files are too big

Problem:    Some source files are too big.
Solution:   Move buffer and window related functions to evalbuffer.c and
            evalwindow.c. (Yegappan Lakshmanan, closes #4898)
diff --git a/src/Make_morph.mak b/src/Make_morph.mak
index 09e514c..3f896da 100644
--- a/src/Make_morph.mak
+++ b/src/Make_morph.mak
@@ -41,8 +41,10 @@
 	digraph.c						\
 	edit.c							\
 	eval.c							\
+	evalbuffer.c						\
 	evalfunc.c						\
 	evalvars.c						\
+	evalwindow.c						\
 	ex_cmds.c						\
 	ex_cmds2.c						\
 	ex_docmd.c						\