patch 8.1.1933: the eval.c file is too big

Problem:    The eval.c file is too big.
Solution:   Move code related to variables to evalvars.c. (Yegappan
            Lakshmanan, closes #4868)
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index facc15e..8050f32 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -731,6 +731,7 @@
 	$(OUTDIR)\edit.obj \
 	$(OUTDIR)\eval.obj \
 	$(OUTDIR)\evalfunc.obj \
+	$(OUTDIR)\evalvars.obj \
 	$(OUTDIR)\ex_cmds.obj \
 	$(OUTDIR)\ex_cmds2.obj \
 	$(OUTDIR)\ex_docmd.obj \
@@ -1486,6 +1487,8 @@
 
 $(OUTDIR)/evalfunc.obj:	$(OUTDIR) evalfunc.c  $(INCL)
 
+$(OUTDIR)/evalvars.obj:	$(OUTDIR) evalvars.c  $(INCL)
+
 $(OUTDIR)/ex_cmds.obj:	$(OUTDIR) ex_cmds.c  $(INCL)
 
 $(OUTDIR)/ex_cmds2.obj:	$(OUTDIR) ex_cmds2.c  $(INCL)
@@ -1771,6 +1774,7 @@
 	proto/edit.pro \
 	proto/eval.pro \
 	proto/evalfunc.pro \
+	proto/evalvars.pro \
 	proto/ex_cmds.pro \
 	proto/ex_cmds2.pro \
 	proto/ex_docmd.pro \