Enable GNU libc "memory tracing" when compiled with debug code.

This patch lets ngIRCd activate "memory tracing" of the GNU libc when
compiled with debug code (configure: --enable-debug) and the functionality
is available on the system.
(http://www.gnu.org/software/libc/manual/html_node/Allocation-Debugging.html)

configure.in

@@ -457,6 +457,7 @@ AC_ARG_ENABLE(debug,
 if test "$x_debug_on" = "yes"; then
 	AC_DEFINE(DEBUG, 1)
 	test "$GCC" = "yes" && CFLAGS="-pedantic $CFLAGS"
+	AC_CHECK_FUNCS(mtrace)
 fi
 
 # enable "strict RFC rules"?

src/ngircd/ngircd.c

@@ -84,6 +84,12 @@ main( int argc, const char *argv[] )
 	int i;
 	size_t n;
 
+#if defined(DEBUG) && defined(HAVE_MTRACE)
+	/* enable GNU libc memory tracing when running in debug mode
+	 * and functionality available */
+	mtrace();
+#endif
+
 	umask( 0077 );
 
 	NGIRCd_SignalQuit = NGIRCd_SignalRestart = NGIRCd_SignalRehash = false;