Rename poll to poll_oneoff, and remove __wasi_subrwflags_t.

Renaming `poll` avoids a conflict with the libc poll in implementations
where libc shared a namespace with the wasi syscall names. And calling
it "oneoff" makes it clear that this is the classic poll which unlike
things like epoll doesn't have a way to factor out the
per-file-descriptor overhead over multiple calls.

__wasi_subrwflags_t was unused and its only value was deprecated.

Author: sunfishcode

expected/wasm32-wasi/undefined-symbols.txt

@@ -51,7 +51,7 @@ __wasi_file_stat_get
 __wasi_file_stat_put
 __wasi_file_symlink
 __wasi_file_unlink
-__wasi_poll
+__wasi_poll_oneoff
 __wasi_proc_exit
 __wasi_random_get
 __wasi_sched_yield

libc-bottom-half/cloudlibc/src/libc/poll/poll.c

@@ -75,7 +75,7 @@ int poll(struct pollfd *fds, size_t nfds, int timeout) {
   // Execute poll().
   __wasi_event_t events[nevents];
   __wasi_errno_t error =
-      __wasi_poll(subscriptions, events, nevents, &nevents);
+      __wasi_poll_oneoff(subscriptions, events, nevents, &nevents);
   if (error != 0) {
     errno = error;
     return -1;

libc-bottom-half/cloudlibc/src/libc/sys/ioctl/ioctl.c

@@ -34,7 +34,7 @@ int ioctl(int fildes, int request, ...) {
       };
       __wasi_event_t events[__arraycount(subscriptions)];
       size_t nevents;
-      __wasi_errno_t error = __wasi_poll(
+      __wasi_errno_t error = __wasi_poll_oneoff(
           subscriptions, events, __arraycount(subscriptions), &nevents);
       if (error != 0) {
         errno = error;

libc-bottom-half/cloudlibc/src/libc/sys/select/pselect.c

@@ -104,7 +104,7 @@ int pselect(int nfds, fd_set *restrict readfds, fd_set *restrict writefds,
   // Execute poll().
   __wasi_event_t events[nevents];
   __wasi_errno_t error =
-      __wasi_poll(subscriptions, events, nevents, &nevents);
+      __wasi_poll_oneoff(subscriptions, events, nevents, &nevents);
   if (error != 0) {
     errno = error;
     return -1;

libc-bottom-half/cloudlibc/src/libc/time/clock_nanosleep.c

@@ -44,6 +44,6 @@ int clock_nanosleep(clockid_t clock_id, int flags, const struct timespec *rqtp,
   // Block until polling event is triggered.
   size_t nevents;
   __wasi_event_t ev;
-  __wasi_errno_t error = __wasi_poll(&sub, &ev, 1, &nevents);
+  __wasi_errno_t error = __wasi_poll_oneoff(&sub, &ev, 1, &nevents);
   return error == 0 && ev.error == 0 ? 0 : ENOTSUP;
 }

libc-bottom-half/headers/public/wasi.h

@@ -735,12 +735,12 @@ __wasi_errno_t __wasi_file_unlink(
     __wasi_ulflags_t flags
 ) __WASI_SYSCALL_NAME(file_unlink) __attribute__((__warn_unused_result__));
 
-__wasi_errno_t __wasi_poll(
+__wasi_errno_t __wasi_poll_oneoff(
     const __wasi_subscription_t *in,
     __wasi_event_t *out,
     size_t nsubscriptions,
     size_t *nevents
-) __WASI_SYSCALL_NAME(poll) __attribute__((__warn_unused_result__));
+) __WASI_SYSCALL_NAME(poll_oneoff) __attribute__((__warn_unused_result__));
 
 _Noreturn void __wasi_proc_exit(
     __wasi_exitcode_t rval