get_nprocs: Only return explictly set cache values (BZ #16996)

The implementation of __get_nprocs uses a stactic variable to cache
the value of the current number of processors.  The caching breaks when
'time (NULL) == 0':

  $ cat nproc.c
  #include <stdio.h>
  #include <time.h>
  #include <sys/time.h>

  int main(int argc, char *argv[])
  {
    time_t t;
    struct timeval tv = {0, 0};
    printf("settimeofday({0, 0}, NULL) = %d\n", settimeofday(&tv, NULL));
    t = time(NULL);
    printf("Time: %d, CPUs: %d\n", (unsigned int)t, get_nprocs());
    return 0;
  }
  $ gcc -O3 nproc.c
  $ ./a.out
  settimeofday({0, 0}, NULL) = -1
  Time: 1401311578, CPUs: 4
  $ sudo ./a.out
  settimeofday({0, 0}, NULL) = 0
  Time: 0, CPUs: 0

The problem is with the condition used to check whether a cached
value should be returned or not:

  static int cached_result;
  static time_t timestamp;

  time_t now = time (NULL);
  time_t prev = timestamp;
  atomic_read_barrier ();
  if (now == prev)
    return cached_result;

This patch fixes the problem by ensuring that 'cached_result' has
been set at least once before returning it.
Add a fast path for C rd/wrlock v2

One difference of the C versions to the assembler wr/rdlock
is that the C compiler saves some registers which are unnecessary
for the fast path in the prologue of the functions. Split the
uncontended fast path out into a separate function. Only when contention is
detected is the full featured function called. This makes
the fast path code (nearly) identical to the assembler version,
and gives uncontended performance within a few cycles.

v2: Rename some functions and add space.
Add adaptive elision to rwlocks

This patch relies on the C version of the rwlocks posted earlier.
With C rwlocks it is very straight forward to do adaptive elision
using TSX. It is based on the infrastructure added earlier
for mutexes, but uses its own elision macros. The macros
are fairly general purpose and could be used for other
elision purposes too.

This version is much cleaner than the earlier assembler based
version, and in particular implements adaptation which makes
it safer.

I changed the behavior slightly to not require any changes
in the test suite and fully conform to all expected
behaviors (generally at the cost of not eliding in
various situations). In particular this means the timedlock
variants are not elided.  Nested trylock aborts.
Remove x86 assembler rwlock code

With the recent tuning the C version of rwlocks is basically the same
performance as the x86 assembler version for uncontended locks (with a
a few cycles near the run-to-run variability). For others it should not
matter anyways.

So remove the assembler code and use the C version like other
architectures.
ChangeLog fix
m68k: avoid pointer to integer conversion warning
Consolidate sparc clone, fork, and vfork implementations.

	* nptl/sysdeps/unix/sysv/linux/sparc/sparc32/clone.S: Delete.
	* nptl/sysdeps/unix/sysv/linux/sparc/sparc32/pt-vfork.S: Delete.
	* nptl/sysdeps/unix/sysv/linux/sparc/sparc32/vfork.S: Moved ...
	* sysdeps/unix/sysv/linux/sparc/sparc32/vfork.S: ... here.
	* nptl/sysdeps/unix/sysv/linux/sparc/sparc64/clone.S: Delete.
	* nptl/sysdeps/unix/sysv/linux/sparc/sparc64/pt-vfork.S: Delete.
	* nptl/sysdeps/unix/sysv/linux/sparc/sparc64/vfork.S: Moved ...
	* sysdeps/unix/sysv/linux/sparc/sparc64/vfork.S: ... here.
	* sysdeps/unix/sysv/linux/sparc/fork.S: Delete.
	* sysdeps/unix/sysv/linux/sparc/pt-vfork.S: New file.
	* sysdeps/unix/sysv/linux/sparc/sparc32/clone.S (__thread_start):
	Remove RESET_PID cpp guards.
	* sysdeps/unix/sysv/linux/sparc/sparc64/clone.S (__thread_start):
	Remove RESET_PID cpp guards.
	* sysdeps/unix/sysv/linux/sparc/vfork.S: Delete.
S390: Convert fork.c to arch-fork.h
Move S390 code out of nptl/sysdeps/s390/.
S390: Move NPTL public headers to sysdeps/s390/nptl/.
Fix pthread.h in installed-headers list.