Tweak to `button' face in custom themes.

* etc/themes/dichromacy-theme.el:
* etc/themes/tango-theme.el:
* etc/themes/tango-dark-theme.el:
* etc/themes/wheatgrass-theme.el: Don't define button face separately;
it inherits from link now.

etc/ChangeLog

+2011-07-07  Chong Yidong  <cyd@stupidchicken.com>
+
+	* themes/dichromacy-theme.el:
+	* themes/tango-theme.el:
+	* themes/tango-dark-theme.el:
+	* themes/wheatgrass-theme.el: Don't define button face separately;
+	it inherits from link now.
+
 2011-07-06  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
 	* NEWS: Clarify that `smtpmail-starttls-credentials' doesn't exist.

etc/themes/dichromacy-theme.el

@@ -72,7 +72,6 @@ Ansi-Color faces are included.")
    `(font-lock-warning-face ((,class (:weight bold :slant italic
 				      :foreground ,vermillion))))
    ;; Button and link faces
-   `(button ((,class (:underline t :foreground ,blue))))
    `(link ((,class (:underline t :foreground ,blue))))
    `(link-visited ((,class (:underline t :foreground ,redpurple))))
    ;; Gnus faces

etc/themes/tango-dark-theme.el

@@ -86,7 +86,6 @@ Semantic, and Ansi-Color faces are included.")
    `(font-lock-variable-name-face ((,class (:foreground ,orange-1))))
    `(font-lock-warning-face ((,class (:foreground ,red-0))))
    ;; Button and link faces
-   `(button ((,class (:underline t :foreground ,blue-1))))
    `(link ((,class (:underline t :foreground ,blue-1))))
    `(link-visited ((,class (:underline t :foreground ,blue-2))))
    ;; Gnus faces

etc/themes/tango-theme.el

@@ -77,7 +77,6 @@ Semantic, and Ansi-Color faces are included.")
    `(font-lock-variable-name-face ((,class (:foreground ,orange-4))))
    `(font-lock-warning-face ((,class (:foreground ,red-2))))
    ;; Button and link faces
-   `(button ((,class (:underline t :foreground ,blue-3))))
    `(link ((,class (:underline t :foreground ,blue-3))))
    `(link-visited ((,class (:underline t :foreground ,blue-2))))
    ;; Gnus faces

etc/themes/wheatgrass-theme.el

@@ -47,7 +47,6 @@ of green, brown, and blue.")
    `(font-lock-variable-name-face ((,class (:foreground "yellow green"))))
    `(font-lock-warning-face ((,class (:foreground "salmon1"))))
    ;; Button and link faces
-   `(button ((,class (:underline t :foreground "cyan"))))
    `(link ((,class (:underline t :foreground "cyan"))))
    `(link-visited ((,class (:underline t :foreground "dark cyan"))))
    ;; Gnus faces