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_cyg_ming.mak b/src/Make_cyg_ming.mak
index 9f86cef..bd2dba2 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -721,8 +721,10 @@
 	$(OUTDIR)/digraph.o \
 	$(OUTDIR)/edit.o \
 	$(OUTDIR)/eval.o \
+	$(OUTDIR)/evalbuffer.o \
 	$(OUTDIR)/evalfunc.o \
 	$(OUTDIR)/evalvars.o \
+	$(OUTDIR)/evalwindow.o \
 	$(OUTDIR)/ex_cmds.o \
 	$(OUTDIR)/ex_cmds2.o \
 	$(OUTDIR)/ex_docmd.o \