Remove no longer needed workaround which breaks node.js build.

diff -u -r ../libuv-v1.7.3/include/pthread-fixes.h ./include/pthread-fixes.h
--- ../libuv-v1.7.3/include/pthread-fixes.h	2015-08-27 17:42:36.000000000 -0400
+++ ./include/pthread-fixes.h	2015-09-08 17:31:47.658023853 -0400
@@ -57,16 +57,4 @@
 
 int pthread_yield(void);
 
-/* Workaround pthread_sigmask() returning EINVAL on versions < 4.1 by
- * replacing all calls to pthread_sigmask with sigprocmask. See:
- * https://android.googlesource.com/platform/bionic/+/9bf330b5
- * https://code.google.com/p/android/issues/detail?id=15337
- */
-int uv__pthread_sigmask(int how, const sigset_t* set, sigset_t* oset);
-
-#ifdef pthread_sigmask
-#undef pthread_sigmask
-#endif
-#define pthread_sigmask(how, set, oldset) uv__pthread_sigmask(how, set, oldset)
-
 #endif  /* GOOGLE_BREAKPAD_COMMON_ANDROID_TESTING_PTHREAD_FIXES_H */
diff -u -r ../libuv-v1.7.3/src/unix/pthread-fixes.c ./src/unix/pthread-fixes.c
--- ../libuv-v1.7.3/src/unix/pthread-fixes.c	2015-08-27 17:42:36.000000000 -0400
+++ ./src/unix/pthread-fixes.c	2015-09-08 17:31:31.562244293 -0400
@@ -29,31 +29,6 @@
    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-/* Android versions < 4.1 have a broken pthread_sigmask.
- * Note that this block of code must come before any inclusion of
- * pthread-fixes.h so that the real pthread_sigmask can be referenced.
- * */
-#include <errno.h>
-#include <pthread.h>
-#include <signal.h>
-
-int uv__pthread_sigmask(int how, const sigset_t* set, sigset_t* oset) {
-  static int workaround;
-
-  if (workaround) {
-    return sigprocmask(how, set, oset);
-  } else if (pthread_sigmask(how, set, oset)) {
-    if (errno == EINVAL && sigprocmask(how, set, oset) == 0) {
-      workaround = 1;
-      return 0;
-    } else {
-      return -1;
-    }
-  } else {
-    return 0;
-  }
-}
-
 /*Android doesn't provide pthread_barrier_t for now.*/
 #ifndef PTHREAD_BARRIER_SERIAL_THREAD