build: Fix DPKG_CHECK_DEFINE to properly check for dpkg_cv_define_$1

The macro was checking for the dpkg_cv_define variable, which implied
always doing an AC_DEFINE to 0.

As a consequence now start-stop-deaemon will use TIOCNOTTY when
available.

debian/changelog

@@ -28,6 +28,7 @@ dpkg (1.15.5) UNRELEASED; urgency=low
     memory usage when handling lots of symlinks, and be slightly faster.
   * Rework varbuf api to avoid increasing buffers indefinitely when adding
     content to them, regardless of space being already available.
+  * Fix build macros to allow start-stop-deaemon to use TIOCNOTTY.
 
   [ Raphaël Hertzog ]
   * Add versioned dependency on base-files (>= 5.0.0) to dpkg-dev to ensure

m4/types.m4

@@ -43,7 +43,7 @@ AC_DEFUN([DPKG_CHECK_DEFINE],
 	[AC_LANG_PROGRAM([[#include <$2>]], [[int i = $1;]])],
 	[dpkg_cv_define_$1=yes],
 	[dpkg_cv_define_$1=no])])
-AS_IF([test "x$dpkg_cv_define" = "xyes"],
+AS_IF([test "x$dpkg_cv_define_$1" = "xyes"],
 	[AC_DEFINE([HAVE_]$1, 1, [Define to 1 if you have the macro ']$1[' in
 				  <$2>, and to 0 if you don't.])],
 	[AC_DEFINE([HAVE_]$1, 0)])[]dnl