ntdll: Use the gettid system call on all Linux platforms.

dlls/ntdll/server.c

@@ -51,6 +51,9 @@
 #ifdef HAVE_SYS_STAT_H
 # include <sys/stat.h>
 #endif
+#ifdef HAVE_SYS_SYSCALL_H
+# include <sys/syscall.h>
+#endif
 #ifdef HAVE_SYS_UIO_H
 #include <sys/uio.h>
 #endif
@@ -943,10 +946,8 @@ static void send_server_task_port(void)
 static int get_unix_tid(void)
 {
     int ret = -1;
-#if defined(linux) && defined(__i386__)
-    ret = syscall(224 /*SYS_gettid*/);
-#elif defined(linux) && defined(__x86_64__)
-    ret = syscall(186 /*SYS_gettid*/);
+#ifdef linux
+    ret = syscall( SYS_gettid );
 #elif defined(__sun)
     ret = pthread_self();
 #elif defined(__APPLE__)