Define GPGEdit{Options,Recipients} autocmd in their own group

This allows them to be properly cleared only when the buffer is
re-created/loaded.  This fixes the handling of the autocmds when the
Edit buffer is saved, but not hidden or deleted.

The autocmd remains in place, rather than having an acwrite buffer with
no autocmd set.

Signed-off-by: James McCoy <jamessan@jamessan.com>

autoload/gnupg.vim

@@ -680,8 +680,11 @@ function gnupg#edit_recipients()
   endif
 
   if s:NewInputBuffer('GPGRecipients')
+    augroup GPGRecipients
+      au! * <buffer>
       " add a autocommand to regenerate the recipients after a write
       autocmd BufHidden,BufUnload,BufWriteCmd <buffer> call s:GPGFinishRecipientsBuffer()
+    augroup END
 
     " put some comments to the scratch buffer
     silent put ='GPG: ----------------------------------------------------------------------'
@@ -767,9 +770,6 @@ function s:GPGFinishRecipientsBuffer()
     execute 'silent! ' . bufwinnr(expand("<afile>:p")) . "wincmd w"
   endif
 
-  " delete the autocommand
-  autocmd! * <buffer>
-
   " get the recipients from the scratch buffer
   let recipients = []
   let lines = getline(1,"$")
@@ -856,8 +856,11 @@ function gnupg#edit_options()
 
   " only do this if it isn't already a GPGOptions_* buffer
   if s:NewInputBuffer('GPGOptions')
+    augroup GPGOptions
+      au! * <buffer>
       " add a autocommand to regenerate the options after a write
       autocmd BufHidden,BufUnload,BufWriteCmd <buffer> call s:GPGFinishOptionsBuffer()
+    augroup END
 
     " put some comments to the scratch buffer
     silent put ='GPG: ----------------------------------------------------------------------'
@@ -916,9 +919,6 @@ function s:GPGFinishOptionsBuffer()
   let options = []
   let unknownOptions = []
 
-  " delete the autocommand
-  autocmd! * <buffer>
-
   " get the options from the scratch buffer
   let lines = getline(1, "$")
   for option in lines