generic compat_sys_rt_sigpending()

conditional on GENERIC_COMPAT_RT_SIGPENDING; by the end of that series
it will become the same thing as COMPAT and conditional will die out.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/Kconfig b/arch/Kconfig
index 374a68a..18c0383 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -362,6 +362,9 @@
 config GENERIC_COMPAT_RT_SIGPROCMASK
 	bool
 
+config GENERIC_COMPAT_RT_SIGPENDING
+	bool
+
 #
 # ABI hall of shame
 #