if optimization and eating trailing whitespace with dnl

[Mike Frysinger]

the lcd4linux package uses a common construct like so:

AC_INIT
if :; then
        AC_MSG_RESULT([no])
        AC_MSG_ERROR([blah blah blah
blah blah
])dnl
fi
AC_OUTPUT

with the latest autoconf, this creates a shell script with a syntax error:
$ autoconf && bash -n configure
configure: line 2363: syntax error: unexpected end of file

if the dnl is dropped, or a newline is added before the fi, then the generated 
script works fine.  the generate code with the newline consumed looks like:
blah blah
" "$LINENO" 5fi

the source for the latest lcd4linux can be found here:
http://ssl.bulix.org/projects/lcd4linux/attachment/wiki/Download/lcd4linux-0.10.1-
RC2.tar.gz
-mike