reorganize pthread data structures and move the definitions to alltypes.h

this allows sys/types.h to provide the pthread types, as required by
POSIX. this design also facilitates forcing ABI-compatible sizes in
the arch-specific alltypes.h, while eliminating the need for
developers changing the internals of the pthread types to poke around
with arch-specific headers they may not be able to test.

src/internal/pthread_impl.h

@@ -38,6 +38,25 @@ struct pthread {
 	pthread_attr_t attr;
 };
 
+#define __SU (sizeof(size_t)/sizeof(int))
+
+#define _a_stacksize __u.__s[0]
+#define _a_guardsize __u.__s[1]
+#define _a_detach __u.__i[2*__SU+0]
+#define _m_type __u.__i[0]
+#define _m_lock __u.__i[1]
+#define _m_waiters __u.__i[2]
+#define _m_owner __u.__i[3]
+#define _c_block __u.__i[0]
+#define _rw_wrlock __u.__i[0]
+#define _rw_readers __u.__i[1]
+#define _rw_waiters __u.__i[2]
+#define _rw_owner __u.__i[3]
+#define _b_count __u.__i[0]
+#define _b_limit __u.__i[1]
+#define _b_left __u.__i[2]
+#define _b_waiters __u.__i[3]
+
 #include "pthread_arch.h"
 
 #define SIGCANCEL 32