include: define _DEFAULT_SOURCE

Since glibc 2.20, the _BSD_SOURCE and _SVID_SOURCE macros are
deprecated in favor of the _DEFAULT_SOURCE macro.

See https://sourceware.org/glibc/wiki/Release/2.20#Packaging_Changes

Change-Id: I18dd6a698f3f5aa51d1e45bf53b031bb061e17e8
Reviewed-on: https://plan9port-review.googlesource.com/1500
Reviewed-by: David du Colombier <0intro@gmail.com>

include/u.h

@@ -19,6 +19,7 @@ extern "C" {
 #define _BSD_SOURCE 1
 #define _NETBSD_SOURCE 1	/* NetBSD */
 #define _SVID_SOURCE 1
+#define _DEFAULT_SOURCE 1
 #if !defined(__APPLE__) && !defined(__OpenBSD__)
 #	define _XOPEN_SOURCE 1000
 #	define _XOPEN_SOURCE_EXTENDED 1

src/cmd/grap/main.c

@@ -1,4 +1,5 @@
 #define _BSD_SOURCE 1	/* strdup, mkstemp */
+#define _DEFAULT_SOURCE 1
 #include <stdio.h>
 #include <signal.h>
 #include <math.h>

src/cmd/rio/menu.c

@@ -4,6 +4,7 @@
 
 /* Copyright (c) 1994-1996 David Hogan, see README for licence details */
 #define _SVID_SOURCE 1	/* putenv in glibc */
+#define _DEFAULT_SOURCE 1
 #include <stdio.h>
 #include <signal.h>
 #include <unistd.h>

src/cmd/troff/n2.c

@@ -5,6 +5,7 @@
  */
 
 #define _BSD_SOURCE 1	/* popen */
+#define _DEFAULT_SOURCE 1
 #include "tdef.h"
 #include "fns.h"
 #include "ext.h"

src/cmd/troff/n7.c

@@ -1,4 +1,5 @@
 #define _BSD_SOURCE 1	/* isascii */
+#define _DEFAULT_SOURCE 1
 #include "tdef.h"
 #include "fns.h"
 #include "ext.h"

src/lib9/utf/utfecpy.c

@@ -12,6 +12,7 @@
  * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
  */
 #define _BSD_SOURCE 1	/* memccpy */
+#define _DEFAULT_SOURCE 1
 #include <stdarg.h>
 #include <string.h>
 #include "plan9.h"