New default for `org-file-apps'.

The new default asks to open all those files in Emacs, for which
`auto-mode-alist' does contain an entry.  The reasoning is that
Org-mode users are Emacs users and probably like to use exactly
this setup.  The only exception configured as such by default is
that files with html or xhtml extensions will be opened using
the system default, most likely a browser.

lisp/org-exp.el

@@ -1476,7 +1476,6 @@ on this string to produce the exported version."
       (when (plist-get parameters :emph-multiline)
 	(org-export-concatenate-multiline-emphasis))
 
-
       ;; Remove special table lines
       (when org-export-table-remove-special-lines
 	(org-export-remove-special-table-lines))

lisp/org.el

@@ -1138,13 +1138,8 @@ See `org-file-apps'.")
 
 (defcustom org-file-apps
   '(
-    ("txt" . emacs)
-    ("tex" . emacs)
-    ("ltx" . emacs)
-    ("org" . emacs)
-    ("el"  . emacs)
-    ("bib" . emacs)
     (auto-mode . emacs)
+    ("\\.x?html?\\'" . default)
     )
   "External applications for opening `file:path' items in a document.
 Org-mode uses system defaults for different file types, but
@@ -1159,12 +1154,16 @@ file identifier are
                because external applications cannot handle such paths.
 `auto-mode'    Matches files that are mached by any entry in `auto-mode-alist',
                so all files Emacs knows how to handle.  Useing this with
-               command `emacs' will open most files in Emacs.
+               command `emacs' will open most files in Emacs.  Beware that this
+               will also open html files insite Emacs, unless you add
+               (\"html\" . default) to the list as well.
  t             Default for files not matched by any of the other options.
 
 Possible values for the command are:
  `emacs'       The file will be visited by the current Emacs process.
- `default'     Use the default application for this file type.
+ `default'     Use the default application for this file type, which is the
+               association for t in the list, most likely in the system-specific
+               part.
                This can be used to overrule an unwanted seting in the
                system-specific variable.
  string        A command to be executed by a shell; %s will be replaced