Add alignment to opaque types.

If there is no alignment forced, then the compiler might put these
structures at any alignment.

Change-Id: I6416db72433504e0ec1178bfae6f5b18b6e363fb

libc/include/pthread.h

@@ -78,7 +78,7 @@ typedef struct {
 #else
   char __private[4];
 #endif
-} pthread_cond_t;
+} pthread_cond_t __attribute__((aligned(8)));
 
 #define PTHREAD_COND_INITIALIZER  { { 0 } }
 
@@ -93,7 +93,7 @@ typedef struct {
 #else
   char __private[40];
 #endif
-} pthread_rwlock_t;
+} pthread_rwlock_t __attribute__((aligned(8)));
 
 #define PTHREAD_RWLOCK_INITIALIZER  { { 0 } }