docs: document zsh specialty with empty here-documents.

[Ralf Wildenhues]

<http://thread.gmane.org/gmane.comp.gnu.libtool.patches/10647>

OK?  The AT_DATA documentation already specifies that $2 should end in a
newlines, so that part didn't need an update.

Thanks,
Ralf

    docs: document zsh specialty with empty here-documents.
    
    * doc/autoconf.texi (Here-Documents): zsh 4.3.10 adds a newline
    to empty here-docs.

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index e8d65cb..344aefa 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -14897,6 +14897,15 @@ Here-Documents
 @samp{ksh93g} (1998-04-30) but as of 2006 many operating systems were
 still shipping older versions with the bug.
 
+Empty here-documents are not portable either: @command{zsh} 4.3.10 creates
+a file with a single newline upon, whereas other shells create an empty
+file, upon:
+
address@hidden
+cat >file <<EOF
+EOF
address@hidden example
+
 Many shells (including the Bourne shell) implement here-documents
 inefficiently.  In particular, some shells can be extremely inefficient when
 a single statement contains many here-documents.  For instance if your