Account for alloca use when collecting interface addresses (bug 16002)

To reproduce:

	# ip li add name dummy0 type dummy
	# site_id=$(head -c6 /dev/urandom | od -tx2 -An | tr ' ' ':')
	# for ((i = 0; i < 65536; i++)) do
	> ip ad ad $(printf fd80$site_id::%04x $i)/128 dev dummy0
	> done
	# (ulimit -s 900; getent ahosts localhost)
	# ip li de dummy0
benchtests: Move bench.py to benchtests/scripts/

It makes much more sense to have all benchmarking-related scripts in a
single place away from everything else.
Fix use of half-initialized result in getaddrinfo when using nscd (bug 16743)

This fixes a bug in the way the results from __nscd_getai are collected:
for every returned result a new entry is first added to the
gaih_addrtuple list, but if that result doesn't match the request this
entry remains uninitialized.  So for this non-matching result an extra
result with uninitialized content is returned.

To reproduce (with nscd running):

	$ getent ahostsv4 localhost
	127.0.0.1       STREAM localhost
	127.0.0.1       DGRAM
	127.0.0.1       RAW
	(null)          STREAM
	(null)          DGRAM
	(null)          RAW
S390: Fix -Wundef warning for __PTHREAD_MUTEX_HAVE_ELISION.
Use += before-compile instead of a :=.
S390: Correct type of sa_flags in struct sigaction for POSIX conformance
(BZ #16713).
S390: Define SIZE_MAX as unsigned long (BZ #16712).
S390: Fix namespace violation in struct stat (BZ #16714).