Fix CR expansion & syn fold enabled by InsertLeave

Benamin Fritz reported the following:

Without the "zv", if the user has syntax folding on, when the mapping
invokes <Esc> the pair of braces which were just separated by a <CR>
could become folded, so that the trailing "o" opens a new line AFTER
the pair.

autoload/delimitMate.vim

@@ -418,7 +418,9 @@ function! delimitMate#ExpandReturn() "{{{
 
 		" Not sure why I used the previous combos, but I'm sure somebody will tell
 		" me about it.
-		return "\<Esc>a\<CR>\<Esc>O"
+		" XXX zv prevents breaking expansion with syntax folding enabled by
+		" InsertLeave.
+		return "\<Esc>a\<CR>\<Esc>zvO"
 	else
 		return "\<CR>"
 	endif

test/expand_cr.txt

@@ -46,5 +46,20 @@ sub foo {
 call setline(1, "\"{bracketed}")
 normal A"x
 ================================================================================
-"{bracketed}"x
+"{bracketed""x
+--------------------------------------------------------------------------------
+# Syntax folding enabled by autocmd breaks expansion. But ti can't be tested
+# with :normal
+new
+autocmd InsertEnter * let w:fdm=&foldmethod | setl foldmethod=manual
+autocmd InsertLeave * let &foldmethod = w:fdm
+set foldmethod=marker
+set foldmarker={,}
+set foldlevel=0
+set backspace=2
+exec "normal iabc {\<CR>x"
+================================================================================
+abc {
+    x
+}
 --------------------------------------------------------------------------------