patch 8.1.1943: more code can be moved to evalvars.c

Problem:    More code can be moved to evalvars.c.
Solution:   Move it, clean up comments.  Also move some window related
            functions to window.c. (Yegappan Lakshmanan, closes #4874)
diff --git a/src/proto/evalvars.pro b/src/proto/evalvars.pro
index 6226d43..fdb2e34 100644
--- a/src/proto/evalvars.pro
+++ b/src/proto/evalvars.pro
@@ -58,7 +58,9 @@
 void f_gettabvar(typval_T *argvars, typval_T *rettv);
 void f_gettabwinvar(typval_T *argvars, typval_T *rettv);
 void f_getwinvar(typval_T *argvars, typval_T *rettv);
+void f_getbufvar(typval_T *argvars, typval_T *rettv);
 void f_settabvar(typval_T *argvars, typval_T *rettv);
 void f_settabwinvar(typval_T *argvars, typval_T *rettv);
 void f_setwinvar(typval_T *argvars, typval_T *rettv);
+void f_setbufvar(typval_T *argvars, typval_T *rettv);
 /* vim: set ft=c : */