Declare variable aliases before their referent

Since Emacs 27 the byte-compiler tells us to do that.
The warning is shown by `byte-compile-file-form-defvar-function',
which contains a comment providing this justification:

Variable aliases are better declared before the corresponding variable,
since it makes it more likely that only one of the two vars has a value
before the `defvaralias' gets executed, which avoids the need to
merge values.

Author: tarsius

markdown-mode.el

@@ -2122,6 +2122,14 @@ Depending on your font, some reasonable choices are:
          ,@(when markdown-hide-markup
              `(display ,markdown-footnote-display))))
 
+(define-obsolete-variable-alias
+ 'gfm-font-lock-keywords
+ 'markdown-mode-font-lock-keywords "v2.4")
+
+(define-obsolete-variable-alias
+ 'markdown-mode-font-lock-keywords-basic
+ 'markdown-mode-font-lock-keywords "v2.4")
+
 (defvar markdown-mode-font-lock-keywords
   `((markdown-match-yaml-metadata-begin . ((1 'markdown-markup-face)))
     (markdown-match-yaml-metadata-end . ((1 'markdown-markup-face)))
@@ -2227,10 +2235,6 @@ Depending on your font, some reasonable choices are:
     (markdown-match-wiki-link . ((0 'markdown-link-face prepend))))
   "Syntax highlighting for Markdown files.")
 
-(define-obsolete-variable-alias
- 'markdown-mode-font-lock-keywords-basic
- 'markdown-mode-font-lock-keywords "v2.4")
-
 ;; Footnotes
 (defvar markdown-footnote-counter 0
   "Counter for footnote numbers.")
@@ -9627,10 +9631,6 @@ rows and columns and the column alignment."
   (setq-local markdown-table-at-point-p-function 'gfm--table-at-point-p)
   (markdown-gfm-parse-buffer-for-languages))
 
-(define-obsolete-variable-alias
- 'gfm-font-lock-keywords
- 'markdown-mode-font-lock-keywords "v2.4")
-
 
 ;;; Viewing modes =============================================================