Remove _BSD_SOURCE and _SVID_SOURCE.

This is a minimal patch to remove _BSD_SOURCE and _SVID_SOURCE from
the documented user API, making them into aliases for _DEFAULT_SOURCE
with a #warning given, but keeping most of the features.h logic using
those macros and all the exising __USE_* conditionals, on the basis
that all the consequent cleanups will go in followup patches.

Tested x86_64.

	* include/features.h: Update comment documenting feature test
	macros.
	[_BSD_SOURCE || _SVID_SOURCE]: Give #warning.  Define
	_DEFAULT_SOURCE.
	* manual/creature.texi (_BSD_SOURCE): Remove documentation.
	(_SVID_SOURCE): Likewise.
	(_DEFAULT_SOURCE): Update description of default features.
	(Feature Test Macros): Don't mention _SVID_SOURCE in conjunction
	with _GNU_SOURCE.
	* manual/filesys.texi (__ftw_func_t): Do not refer to _BSD_SOURCE.
	(S_ISVTX): Likewise.
	* manual/math.texi (Mathematical Constants): Likewise.
	* manual/signal.texi (Interrupted Primitives): Likewise.
	* manual/startup.texi (putenv): Do not refer to _SVID_SOURCE.
	* math/test-matherr.c (_SVID_SOURCE): Do not define.
	* sysvipc/sys/ipc.h [__USE_SVID && !__USE_XOPEN && __GNUC__ >= 2]:
	Don't refer to _SVID_SOURCE in warning text.

1 files changed, 8 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 0f4b8d4f38..2da97546bf 100644
--- a/NEWS
+++ b/NEWS
@@ -13,6 +13,14 @@ Version 2.20
 
 * The am33 port, which had not worked for several years, has been removed
   from ports.
+
+* The _BSD_SOURCE and _SVID_SOURCE feature test macros are no longer
+  supported; they now act the same as _DEFAULT_SOURCE (but generate a
+  warning).  Except for cases where _BSD_SOURCE enabled BSD interfaces that
+  conflicted with POSIX (support for which was removed in 2.19), the
+  interfaces those macros enabled remain available when compiling with
+  _GNU_SOURCE defined, with _DEFAULT_SOURCE defined, or without any feature
+  test macros defined.
 
 Version 2.19