gh-95174: Handle missing dup() and constants in WASI (GH-95229)

- check for ``dup()`` libc function
- handle missing ``F_DUPFD`` in ``dup2()`` replacement function
- add workaround for WASI libc bug in MSG_TRUNC
- ESHUTDOWN is missing, use EPIPE instead
- POLLPRI is missing, define as 0 (no-op)

Modules/socketmodule.c

@@ -7786,6 +7786,10 @@ PyInit__socket(void)
     PyModule_AddIntMacro(m, MSG_EOR);
 #endif
 #ifdef  MSG_TRUNC
+    // workaround for https://github.com/WebAssembly/wasi-libc/issues/305
+    #if defined(__wasi__) && !defined(__WASI_RIFLAGS_RECV_DATA_TRUNCATED)
+    #  define __WASI_RIFLAGS_RECV_DATA_TRUNCATED 2
+    #endif
     PyModule_AddIntMacro(m, MSG_TRUNC);
 #endif
 #ifdef  MSG_CTRUNC