Thread safety documentation.

for  ChangeLog

	* manual/macros.texi: Introduce macros to document thread
	safety properties.
	* manual/intro.texi: Introduce the properties themselves.
Thread safety documentation.

for ChangeLog

	* manual/argp.texi: Document thread safety properties.
Thread safety documentation.

for  ChangeLog

	* manual/arith.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/charset.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/conf.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/crypt.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/ctype.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/debug.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/errno.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/filesys.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/getopt.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/libdl.texi: New.
Thread safety documentation.

for ChangeLog

	* manual/math.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/job.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/lang.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/llio.texi: Document thread safety properties.
Thread safety documentation.

for  ChangeLog

	* manual/locale.texi: Document thread safety properties.
Thread safety documentation.

for  ChangeLog

	* manual/stdio.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/string.texi: Document thread safety properties.
Thread safety documentation.

for ChangeLog

	* manual/pattern.texi: Document thread safety properties.