Make setting of completefunc/omnifunc optional (issue #15)

See issue #15 on GitHub:
  #15

README.md

@@ -103,6 +103,17 @@ If you want to use the omni completion despite the warnings above, execute the f
 
 Now when you type Control-X Control-O Vim will hang for a moment, after which you should be presented with an enormous list of completion candidates :-)
 
+### The `lua_define_completefunc` option
+
+By default the Lua file type plug-in sets the ['completefunc'] [] option so that Vim can complete Lua keywords, global variables and library members using Control-X Control-U. If you don't want the 'completefunc' option to be changed by the plug-in, you can set this option to zero (false) in your [vimrc script] [vimrc]:
+
+    :let g:lua_define_completefunc = 0
+
+### The `lua_define_omnifunc` option
+
+By default the Lua file type plug-in sets the ['omnifunc'] [] option so that Vim can complete the names of all Lua modules installed on the local system. If you don't want the 'omnifunc' option to be changed by the plug-in, you can set this option to zero (false) in your [vimrc script] [vimrc]:
+
+    :let g:lua_define_omnifunc = 0
 
 ### The `lua_define_completion_mappings` option
 
@@ -118,6 +129,8 @@ This software is licensed under the [MIT license](http://en.wikipedia.org/wiki/M
 © 2013 Peter Odding &lt;<peter@peterodding.com>&gt;.
 
 
+['completefunc']: http://vimdoc.sourceforge.net/htmldoc/options.html#'completefunc'
+['omnifunc']: http://vimdoc.sourceforge.net/htmldoc/options.html#'omnifunc'
 [cfu]: http://vimdoc.sourceforge.net/htmldoc/options.html#%27completefunc%27
 [dll]: http://en.wikipedia.org/wiki/Dynamic-link_library
 [dof]: http://www.lua.org/manual/5.1/manual.html#pdf-dofile
@@ -141,4 +154,5 @@ This software is licensed under the [MIT license](http://en.wikipedia.org/wiki/M
 [shell]: http://peterodding.com/code/vim/shell/
 [tob]: http://vimdoc.sourceforge.net/htmldoc/motion.html#text-objects
 [vim]: http://www.vim.org/
+[vimrc]: http://vimdoc.sourceforge.net/htmldoc/starting.html#vimrc
 [vundle]: https://github.com/gmarik/vundle

autoload/xolox/lua.vim

@@ -1,9 +1,9 @@
 " Vim auto-load script
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: August 19, 2013
+" Last Change: August 31, 2013
 " URL: http://peterodding.com/code/vim/lua-ftplugin
 
-let g:xolox#lua#version = '0.7.12'
+let g:xolox#lua#version = '0.7.13'
 let s:miscdir = expand('<sfile>:p:h:h:h') . '/misc/lua-ftplugin'
 let s:omnicomplete_script = s:miscdir . '/omnicomplete.lua'
 let s:globals_script = s:miscdir . '/globals.lua'

doc/ft_lua.txt

@@ -17,7 +17,9 @@ Contents ~
   9. The |lua_complete_library| option
   10. The |lua_complete_dynamic| option
   11. The |lua_complete_omni| option
-  12. The |lua_define_completion_mappings| option
+  12. The |lua_define_completefunc| option
+  13. The |lua_define_omnifunc| option
+  14. The |lua_define_completion_mappings| option
  4. Contact                                                    |ft_lua-contact|
  5. License                                                    |ft_lua-license|
  6. References                                              |ft_lua-references|
@@ -198,6 +200,26 @@ following command:
 Now when you type Control-X Control-O Vim will hang for a moment, after which
 you should be presented with an enormous list of completion candidates :-)
 
+-------------------------------------------------------------------------------
+The *lua_define_completefunc* option
+
+By default the Lua file type plug-in sets the |'completefunc'| option so that
+Vim can complete Lua keywords, global variables and library members using
+Control-X Control-U. If you don't want the 'completefunc' option to be changed
+by the plug-in, you can set this option to zero (false) in your |vimrc| script:
+>
+  :let g:lua_define_completefunc = 0
+<
+-------------------------------------------------------------------------------
+The *lua_define_omnifunc* option
+
+By default the Lua file type plug-in sets the |'omnifunc'| option so that Vim
+can complete the names of all Lua modules installed on the local system. If you
+don't want the 'omnifunc' option to be changed by the plug-in, you can set this
+option to zero (false) in your |vimrc| script:
+>
+  :let g:lua_define_omnifunc = 0
+<
 -------------------------------------------------------------------------------
 The *lua_define_completion_mappings* option
 

ftplugin/lua.vim

@@ -1,7 +1,7 @@
 " Vim file type plug-in
 " Language: Lua 5.1
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: May 15, 2013
+" Last Change: August 31, 2013
 " URL: http://peterodding.com/code/vim/lua-ftplugin
 
 if exists('b:did_ftplugin')
@@ -24,12 +24,16 @@ let &l:includeexpr = 'xolox#lua#includeexpr(v:fname)'
 call add(s:undo_ftplugin, 'setlocal inc< inex<')
 
 " Enable completion of Lua keywords, globals and library members. {{{1
-setlocal completefunc=xolox#lua#completefunc
-call add(s:undo_ftplugin, 'setlocal completefunc<')
+if xolox#misc#option#get('lua_define_completefunc', 1)
+  setlocal completefunc=xolox#lua#completefunc
+  call add(s:undo_ftplugin, 'setlocal completefunc<')
+endif
 
 " Enable dynamic completion by searching "package.path" and "package.cpath". {{{1
-setlocal omnifunc=xolox#lua#omnifunc
-call add(s:undo_ftplugin, 'setlocal omnifunc<')
+if xolox#misc#option#get('lua_define_omnifunc', 1)
+  setlocal omnifunc=xolox#lua#omnifunc
+  call add(s:undo_ftplugin, 'setlocal omnifunc<')
+endif
 
 " Set a filename filter for the Windows file open/save dialogs. {{{1
 if has('gui_win32') && !exists('b:browsefilter')