linux-user: fix signal.c warning

This patch fixes:

linux-user/signal.c:1403: warning: no previous prototype for 'do_sigreturn_v1'
linux-user/signal.c:1473: warning: no previous prototype for 'do_sigreturn_v2'
linux-user/signal.c:1511: warning: no previous prototype for 'do_rt_sigreturn_v1'
linux-user/signal.c:1552: warning: no previous prototype for 'do_rt_sigreturn_v2'

by making the appropriate functions static.
Signed-off-by: NNathan Froyd <froydnj@codesourcery.com>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6486 c046a42c-6fe2-441c-8c8c-71466251a162

linux-user/signal.c

@@ -1399,7 +1399,7 @@ restore_sigcontext(CPUState *env, struct target_sigcontext *sc)
 	return err;
 }
 
-long do_sigreturn_v1(CPUState *env)
+static long do_sigreturn_v1(CPUState *env)
 {
         abi_ulong frame_addr;
 	struct sigframe_v1 *frame;
@@ -1469,7 +1469,7 @@ static int do_sigframe_return_v2(CPUState *env, target_ulong frame_addr,
     return 0;
 }
 
-long do_sigreturn_v2(CPUState *env)
+static long do_sigreturn_v2(CPUState *env)
 {
         abi_ulong frame_addr;
 	struct sigframe_v2 *frame;
@@ -1507,7 +1507,7 @@ long do_sigreturn(CPUState *env)
     }
 }
 
-long do_rt_sigreturn_v1(CPUState *env)
+static long do_rt_sigreturn_v1(CPUState *env)
 {
         abi_ulong frame_addr;
 	struct rt_sigframe_v1 *frame;
@@ -1548,7 +1548,7 @@ badframe:
 	return 0;
 }
 
-long do_rt_sigreturn_v2(CPUState *env)
+static long do_rt_sigreturn_v2(CPUState *env)
 {
         abi_ulong frame_addr;
 	struct rt_sigframe_v2 *frame;