linux-user/ia64: workaround ia64 strangenesses

ia64 has some strangenesses that need to be workaround:
- it has a __clone2() syscall instead of the using clone() one, with
  different arguments, and which is not declared in the usual headers.
- ucontext.uc_sigmask is declared with type long int, while it is
  actually of type sigset_t.
- uc_mcontext, uc_sigmask, uc_stack, uc_link are declared using #define,
  which clashes with the target_ucontext fields. Change their names to
  tuc_*, as already done for some target architectures.
diff --git a/cpu-exec.c b/cpu-exec.c
index bcfcda2..372aeac 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -81,7 +81,11 @@
     if (puc) {
         /* XXX: use siglongjmp ? */
 #ifdef __linux__
+#ifdef __ia64
+        sigprocmask(SIG_SETMASK, (sigset_t *)&uc->uc_sigmask, NULL);
+#else
         sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL);
+#endif
 #elif defined(__OpenBSD__)
         sigprocmask(SIG_SETMASK, &uc->sc_mask, NULL);
 #endif
@@ -1150,7 +1154,7 @@
     }
     return handle_cpu_signal(ip, (unsigned long)info->si_addr,
                              is_write,
-                             &uc->uc_sigmask, puc);
+                             (sigset_t *)&uc->uc_sigmask, puc);
 }
 
 #elif defined(__s390__)