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/Filelist b/Filelist
index 3ab547a..3ec1acf 100644
--- a/Filelist
+++ b/Filelist
@@ -35,6 +35,7 @@
 		src/edit.c \
 		src/eval.c \
 		src/evalfunc.c \
+		src/evalvars.c \
 		src/ex_cmdidxs.h \
 		src/ex_cmds.c \
 		src/ex_cmds.h \
@@ -188,6 +189,7 @@
 		src/proto/edit.pro \
 		src/proto/eval.pro \
 		src/proto/evalfunc.pro \
+		src/proto/evalvars.pro \
 		src/proto/ex_cmds.pro \
 		src/proto/ex_cmds2.pro \
 		src/proto/ex_docmd.pro \