Replace noreturn with QEMU_NORETURN

Thanks to Robert Riebisch for analysis [1]

[1] http://marc.info/?l=qemu-devel&m=123352293319271&w=2

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6492 c046a42c-6fe2-441c-8c8c-71466251a162
diff --git a/target-i386/exec.h b/target-i386/exec.h
index 2689823..b51667a 100644
--- a/target-i386/exec.h
+++ b/target-i386/exec.h
@@ -63,8 +63,8 @@
                   target_ulong next_eip, int is_hw);
 void do_interrupt_user(int intno, int is_int, int error_code,
                        target_ulong next_eip);
-void noreturn raise_exception_err(int exception_index, int error_code);
-void noreturn raise_exception(int exception_index);
+void QEMU_NORETURN raise_exception_err(int exception_index, int error_code);
+void QEMU_NORETURN raise_exception(int exception_index);
 void do_smm_enter(void);
 
 /* n must be a constant to be efficient */