This synchronization method has a lower overhead and makes
it more likely that the signal arrives during one of the critical
functions.

Also test for fork deadlocks explicitly.

	* All files with FSF copyright notices: Update copyright dates
	using scripts/update-copyrights.
	* locale/programs/charmap-kw.h: Regenerated.
	* locale/programs/locfile-kw.h: Likewise.

	* All files with FSF copyright notices: Update copyright dates
	using scripts/update-copyrights.
	* locale/programs/charmap-kw.h: Regenerated.
	* locale/programs/locfile-kw.h: Likewise.

This patch increases timeouts on some tests I've observed timing out.

elf/tst-tls13 and iconvdata/tst-loading both dynamically load many
objects and so are slow when testing over NFS.  They had timeouts set
from before the default changed from 2 to 20 seconds; this patch
removes those old settings, so effectively increasing the timeout to
20 seconds (from 3 and 10 seconds respectively).

malloc/tst-malloc-thread-fail.c and malloc/tst-mallocfork2.c are slow
on slow systems and so I set a fairly arbitrary 100 second timeout,
which seems to suffice on the system where I saw them timing out.

nss/tst-cancel-getpwuid_r.c and nss/tst-nss-getpwent.c are slow on
systems with a large passwd file; I set timeouts that empirically
worked for me.  (It seems tst-cancel-getpwuid_r.c is hitting the
100000 getpwuid_r call limit in my testing, with each call taking a
bit over 0.007 seconds, so 700 seconds for the test.)

	* elf/tst-tls13.c (TIMEOUT): Remove.
	* iconvdata/tst-loading.c (TIMEOUT): Likewise.
	* malloc/tst-malloc-thread-fail.c (TIMEOUT): Increase to 100.
	* malloc/tst-mallocfork2.c (TIMEOUT): Define to 100.
	* nss/tst-cancel-getpwuid_r.c (TIMEOUT): Define to 900.
	* nss/tst-nss-getpwent.c (TIMEOUT): Define to 300.

The first SIGUSR1 signal could arrive when sigusr1_sender_pid
was still 0.  As a result, kill would send SIGSTOP to the
entire process group.  This would cause the test to hang before
printing any output.

This commit also adds a sched_yield to the signal source, so that
it does not flood the parent process with signals it has never a
chance to handle.

Even with these changes, tst-mallocfork2 still fails reliably
after the fix in commit commit 56290d6e762c1194547e73ff0b948cd79d3a1e03
(Increase fork signal safety for single-threaded processes) is
backed out.

This provides a band-aid and addresses the scenario where fork is
called from a signal handler while the process is in the malloc
subsystem (or has acquired the libio list lock).  It does not
address the general issue of async-signal-safety of fork;
multi-threaded processes are not covered, and some glibc
subsystems have fork handlers which are not async-signal-safe.