system-type related trivia.

* lisp/cedet/semantic/bovine/c.el: Test system-type with memq.

* lisp/progmodes/cperl-mode.el (cperl-find-pods-heres, cperl-write-tags):
No recent Emacs supports system-type `emx'.

* lisp/progmodes/ada-xref.el (is-windows): Rename to ada-on-ms-windows.
(ada-command-separator, ada-default-prj-properties)
(ada-find-any-references): Update for above name change.

* lisp/dirtrack.el (dirtrack-directory-function)
(dirtrack-canonicalize-function):
* lisp/filecache.el (file-cache-completion-ignore-case)
(file-cache-case-fold-search, file-cache-ignore-case):
* lisp/term.el (serial-port-is-file-p): Cosmetic change.

* lisp/emulation/viper-init.el (viper-ms-style-os-p): Doc fix.
Remove non-existent `windows-95' system-type.
* lisp/dired.el (dired-chown-program): Remove non-existent `linux'
system-type.

* lisp/locate.el: Comment.

lisp/progmodes/cperl-mode.el

@@ -3803,7 +3803,8 @@ the sections using `cperl-pod-head-face', `cperl-pod-face',
 						  indentable t))
 	    ;; Need to remove face as well...
 	    (goto-char min)
-	    (and (eq system-type 'emx)
+	    ;; 'emx not supported by Emacs since at least 21.1.
+	    (and (featurep 'xemacs) (eq system-type 'emx)
 		 (eq (point) 1)
 		 (let ((case-fold-search t))
 		   (looking-at "extproc[ \t]")) ; Analogue of #!
@@ -7038,7 +7039,7 @@ Use as
   (or topdir
       (setq topdir default-directory))
   (let ((tags-file-name "TAGS")
-	(case-fold-search (eq system-type 'emx))
+	(case-fold-search (and (featurep 'xemacs) (eq system-type 'emx)))
 	xs rel tm)
     (save-excursion
       (cond (inbuffer nil)		; Already there