[PARISC] Add is_compat_task() helper

... And convert signal.c and ptrace.c to use it instead of open
coded equivalents.

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
diff --git a/include/asm-parisc/compat.h b/include/asm-parisc/compat.h
index 289624d..71b4eee 100644
--- a/include/asm-parisc/compat.h
+++ b/include/asm-parisc/compat.h
@@ -5,6 +5,7 @@
  */
 #include <linux/types.h>
 #include <linux/sched.h>
+#include <linux/personality.h>
 
 #define COMPAT_USER_HZ 100
 
@@ -149,4 +150,14 @@
 	return (void __user *)regs->gr[30];
 }
 
+static inline int __is_compat_task(struct task_struct *t)
+{
+	return personality(t->personality) == PER_LINUX32;
+}
+
+static inline int is_compat_task(void)
+{
+	return __is_compat_task(current);
+}
+
 #endif /* _ASM_PARISC_COMPAT_H */