Prepare to switch to the uapi <linux/signal.h>.

<time.h> didn't need to copy the cruft from <signal.h>, and
<signal.h> only needs the uid_t hack when it's not using
uapi headers.

pthread_exit.cpp should include what it uses.

Change-Id: I836c36abe0f0a781d41fc425b249d1c7686bb124

libc/bionic/pthread_exit.cpp

@@ -28,6 +28,7 @@
 
 #include <pthread.h>
 
+#include <signal.h>
 #include <stdlib.h>
 #include <sys/mman.h>
 

libc/include/signal.h

@@ -39,18 +39,16 @@
 /* For 64-bit, the kernel's struct sigaction doesn't match the POSIX one,
  * so we need to expose our own and translate behind the scenes. */
 #  define sigaction __kernel_sigaction
-#  include <asm/signal.h>
+#  include <linux/signal.h>
 #  undef sigaction
 #else
 /* For 32-bit, we're stuck with the definitions we already shipped,
  * even though they contain a sigset_t that's too small. */
-#  include <asm/signal.h>
+#  define __ARCH_SI_UID_T __kernel_uid32_t /* TODO: remove this when we switch to uapi. */
+#  include <linux/signal.h>
+#  undef __ARCH_SI_UID_T
 #endif
 
-#define __ARCH_SI_UID_T __kernel_uid32_t
-#include <asm/siginfo.h>
-#undef __ARCH_SI_UID_T
-
 __BEGIN_DECLS
 
 typedef int sig_atomic_t;

libc/include/time.h

@@ -32,11 +32,6 @@
 #include <sys/cdefs.h>
 #include <sys/time.h>
 
-/* For struct sigevent. */
-#define __ARCH_SI_UID_T __kernel_uid32_t
-#include <asm/siginfo.h>
-#undef __ARCH_SI_UID_T
-
 __BEGIN_DECLS
 
 #define CLOCKS_PER_SEC 1000000
@@ -45,6 +40,8 @@ extern char* tzname[];
 extern int daylight;
 extern long int timezone;
 
+struct sigevent;
+
 struct tm {
   int tm_sec;
   int tm_min;