Move some pthread functions to signal.h.

POSIX specifies that pthread_kill(3) and pthread_sigmask(3) are
supposed to live in signal.h rather than pthread.h.

Since signal.h now needs pthread_t and pthread_attr_t, I've moved
those defintions into include/machine/pthread_types.h to keep the
namespace clean. I also sorted some includes. The combination of these
two things seems to have exploded into a cascade of missing includes,
so this patch also cleans up all those.

Change-Id: Icfa92a39432fe83f542a797e5a113289d7e4ad0c
diff --git a/libc/bionic/raise.cpp b/libc/bionic/raise.cpp
index f69d90b..0dd0ad7 100644
--- a/libc/bionic/raise.cpp
+++ b/libc/bionic/raise.cpp
@@ -27,6 +27,7 @@
  */
 
 #include <pthread.h>
+#include <signal.h>
 
 int raise(int sig) {
   int rc = pthread_kill(pthread_self(), sig);