Fix Windows build: use WSAPoll instead of poll for linking

lib/platform_compat.h

@@ -103,8 +103,8 @@
     
     // nanosleep already defined in pthread_time.h on MSYS2
     // poll() and pollfd already defined in winsock2.h on MSYS2
-    // Explicitly declare poll() to avoid implicit declaration warning
+    // Use WSAPoll on Windows (available in Vista and later)
-    int poll(struct pollfd *fds, unsigned long nfds, int timeout);
+    #define poll WSAPoll
     
     // sa_family_t might not be defined on some Windows setups
     #ifndef sa_family_t