remove remnants of support for running in no-thread-pointer mode

since 1.1.0, musl has nominally required a thread pointer to be setup.
most of the remaining code that was checking for its availability was
doing so for the sake of being usable by the dynamic linker. as of
commit 71f099cb7d, this is no longer
necessary; the thread pointer is now valid before any libc code
(outside of dynamic linker bootstrap functions) runs.

this commit essentially concludes "phase 3" of the "transition path
for removing lazy init of thread pointer" project that began during
the 1.1.0 release cycle.

src/thread/pthread_cancel.c

@@ -30,7 +30,7 @@ long __syscall_cp_c(syscall_arg_t nr,
 	long r;
 	int st;
 
-	if (!libc.has_thread_pointer || (st=(self=__pthread_self())->canceldisable)
+	if ((st=(self=__pthread_self())->canceldisable)
 	    && (st==PTHREAD_CANCEL_DISABLE || nr==SYS_close))
 		return __syscall(nr, u, v, w, x, y, z);
 
@@ -69,7 +69,6 @@ static void cancel_handler(int sig, siginfo_t *si, void *ctx)
 
 void __testcancel()
 {
-	if (!libc.has_thread_pointer) return;
 	pthread_t self = __pthread_self();
 	if (self->cancel && !self->canceldisable)
 		__cancel();

src/thread/pthread_create.c

@@ -122,7 +122,6 @@ _Noreturn void __pthread_exit(void *result)
 
 void __do_cleanup_push(struct __ptcb *cb)
 {
-	if (!libc.has_thread_pointer) return;
 	struct pthread *self = __pthread_self();
 	cb->__next = self->cancelbuf;
 	self->cancelbuf = cb;
@@ -130,7 +129,6 @@ void __do_cleanup_push(struct __ptcb *cb)
 
 void __do_cleanup_pop(struct __ptcb *cb)
 {
-	if (!libc.has_thread_pointer) return;
 	__pthread_self()->cancelbuf = cb->__next;
 }
 

src/thread/pthread_key_create.c

@@ -13,13 +13,11 @@ int __pthread_key_create(pthread_key_t *k, void (*dtor)(void *))
 {
 	unsigned i = (uintptr_t)&k / 16 % PTHREAD_KEYS_MAX;
 	unsigned j = i;
+	pthread_t self = __pthread_self();
 
-	if (libc.has_thread_pointer) {
-		pthread_t self = __pthread_self();
-		/* This can only happen in the main thread before
-		 * pthread_create has been called. */
-		if (!self->tsd) self->tsd = __pthread_tsd_main;
-	}
+	/* This can only happen in the main thread before
+	 * pthread_create has been called. */
+	if (!self->tsd) self->tsd = __pthread_tsd_main;
 
 	if (!dtor) dtor = nodtor;
 	do {

src/thread/pthread_setcancelstate.c

@@ -3,7 +3,6 @@
 int __pthread_setcancelstate(int new, int *old)
 {
 	if (new > 2U) return EINVAL;
-	if (!libc.has_thread_pointer) return ENOSYS;
 	struct pthread *self = __pthread_self();
 	if (old) *old = self->canceldisable;
 	self->canceldisable = new;