nptl: Add C11 threads call_once functions

This patch adds the call_* definitions from C11 threads (ISO/IEC 9899:2011),
more specifically call_once and required types.

Mostly of the definitions are composed based on POSIX conterparts,including
once_flag (pthread_once_t).  The idea is to make possible to share POSIX
internal implementations for mostly of the code (and making adjustment only
when required).

Checked with a build for all major ABI (aarch64-linux-gnu, alpha-linux-gnu,
arm-linux-gnueabi, i386-linux-gnu, ia64-linux-gnu, m68k-linux-gnu,
microblaze-linux-gnu [1], mips{64}-linux-gnu, nios2-linux-gnu,
powerpc{64le}-linux-gnu, s390{x}-linux-gnu, sparc{64}-linux-gnu,
and x86_64-linux-gnu).

Also ran a full check on aarch64-linux-gnu, x86_64-linux-gnu, i686-linux-gnu,
arm-linux-gnueabhf, and powerpc64le-linux-gnu.

	[BZ #14092]
	* conform/data/threads.h-data (ONCE_FLAG_INIT): New macro.
	(once_flag): New type.
	(call_once): New function.
	* nptl/Makefile (libpthread-routines): Add call_once object.
	* nptl/Versions (libphread) [GLIBC_2.28]: Add call_once symbol.
	* nptl/call_once.c: New file.
	* sysdeps/nptl/threads.h (ONCE_FLAG_INIT): New define.
	(once_flag): New type.
	(call_once): New prototype.

1 files changed, 11 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 1f04a0c649..3d5d1e067a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,17 @@
 2018-07-24  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
 	[BZ #14092]
+	* conform/data/threads.h-data (ONCE_FLAG_INIT): New macro.
+	(once_flag): New type.
+	(call_once): New function.
+	* nptl/Makefile (libpthread-routines): Add call_once object.
+	* nptl/Versions (libphread) [GLIBC_2.28]: Add call_once symbol.
+	* nptl/call_once.c: New file.
+	* sysdeps/nptl/threads.h (ONCE_FLAG_INIT): New define.
+	(once_flag): New type.
+	(call_once): New prototype.
+
+	[BZ #14092]
 	* conform/data/threads.h-data (mtx_plain): New constant.
 	(mtx_recursive): Likewise.
 	(mtx_timed): Likewise.