Rename the WASI module name to "wasi_unstable".

Author: sunfishcode

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

@@ -543,7 +543,7 @@ _Static_assert(sizeof(__wasi_subscription_t) == 56, "non-wasi data layout");
 _Static_assert(_Alignof(__wasi_subscription_t) == 8, "non-wasi data layout");
 
 #define __WASI_SYSCALL_NAME(name) \
-    __attribute__((__import_module__("wasi"), __import_name__(#name)))
+    __attribute__((__import_module__("wasi_unstable"), __import_name__(#name)))
 
 __wasi_errno_t __wasi_clock_res_get(
     __wasi_clockid_t clock_id,