bug#12972: 24.3.50; Move `org-open-file' and associated code out of Org mode

[Drew Adams]

IIUC, `org-open-file' and its associated code, such as `org-file-apps',
`org-default-apps', and `org-apps-regexp-alist', have nothing
particularly to do with Org mode.  They constitute general-purpose code
for opening files using associated programs.  Code that uses them
should not need to load the Org code, and this code should be
maintained separately for general use.
 
Please move all such code out of the Org files and into a more general
file, such as files.el.  Create a new general file for such things, if
that is more appropriate.
 
Anything in the code that is truly specific to Org mode, such as
Org-state mgt and link recognition/following (e.g.,
`org-mark-ring-push', `org-link-frame-setup',
`org-file-apps-entry-match-against-dlink-p', `org-link-search'), should
be kept (only) for Org mode.  What is important is to factor out the
generic code that opens a file using an associated app.
 
Seems like this should have been done when the Org code was added to
Emacs.  There might be additional opportunities for factoring out some
useful, general-purpose code from Org mode - dunno.
 
In GNU Emacs 24.3.50.1 (i386-mingw-nt5.1.2600)
 of 2012-11-19 on MS-W7-DANI
Bzr revision: 110950 monnier@iro.umontreal.ca-20121119182725-5p6w4wjimm7epggr
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -Ic:/emacs/libs/libXpm-3.5.10/include -Ic:/emacs/libs/libXpm-3.5.10/src
 -Ic:/emacs/libs/libpng-1.2.37-lib/include -Ic:/emacs/libs/zlib-1.2.5
 -Ic:/emacs/libs/giflib-4.1.4-1-lib/include
 -Ic:/emacs/libs/jpeg-6b-4-lib/include
 -Ic:/emacs/libs/tiff-3.8.2-1-lib/include
 -Ic:/emacs/libs/libxml2-2.7.8-w32-bin/include/libxml2
 -Ic:/emacs/libs/gnutls-3.0.9-w32-bin/include
 -Ic:/emacs/libs/libiconv-1.9.2-1-lib/include'