Add cross-references to defvar-local

* src/data.c (Fmake_variable_buffer_local):
* src/eval.c (Fdefvar): Add cross-references to 'defvar-local'.

src/data.c

@@ -1819,7 +1819,9 @@ a variable local to the current buffer for one particular use, use
 while setting up a new major mode, unless they have a `permanent-local'
 property.
 
-The function `default-value' gets the default value and `set-default' sets it.  */)
+The function `default-value' gets the default value and `set-default' sets it.
+
+See also `defvar-local'.  */)
   (register Lisp_Object variable)
 {
   struct Lisp_Symbol *sym;

src/eval.c

@@ -818,6 +818,8 @@ The optional argument DOCSTRING is a documentation string for the
 variable.
 
 To define a user option, use `defcustom' instead of `defvar'.
+
+To define a buffer-local variable, use `defvar-local'.
 usage: (defvar SYMBOL &optional INITVALUE DOCSTRING)  */)
   (Lisp_Object args)
 {