test_nptl: replace __sigpause with sigpause

On attempt to build uClibc tests following error message appears:
=========
TEST_LINK nptl/ tst-cancel4
tst-cancel4.c: In function 'tf_sigpause':
tst-cancel4.c:765:3: warning: implicit declaration of function
'__sigpause' [-Wimplicit-function-declaration]
__sigpause (SIGCANCEL, 1);
^
tst-cancel4.o: In function `tf_sigpause':
tst-cancel4.c:(.text+0x1054): undefined reference to `__sigpause'
collect2: error: ld returned 1 exit status
=========

This commit http://git.uclibc.org/uClibc/commit/?id=cef1f9517c319d86b4b426ecc14a10d0fa5494c7
makes __sigpause static limiting its scope to "libc/signal/sigpause.c".

Switching to common implementation "sigpause()" fixes this issue.

Signed-off-by: Alexey Brodkin <Alexey.Brodkin@synopsys.com>

Suggested-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

test/nptl/tst-cancel4.c

@@ -758,11 +758,8 @@ tf_sigpause (void *arg)
 
   pthread_cleanup_push (cl, NULL);
 
-  /* Just for fun block the cancellation signal.  We need to use
-     __xpg_sigpause since otherwise we will get the BSD version.  */
-  //__xpg_sigpause (SIGCANCEL);
-
-  __sigpause (SIGCANCEL, 1);
+  /* Just for fun block the cancellation signal.  */
+  sigpause (SIGCANCEL);
 
   pthread_cleanup_pop (0);