Make SIGRTMIN hide the real-time signals we use internally.

__SIGRTMIN will continue to tell the truth. This matches glibc's
behavior (as evidenced by the fact that we don't need a special case
in the strsignal test now).

Change-Id: I1abe1681d516577afa8cd39c837ef12467f68dd2
diff --git a/libc/kernel/uapi/asm-generic/signal.h b/libc/kernel/uapi/asm-generic/signal.h
index fe7d9a0..a16622a 100644
--- a/libc/kernel/uapi/asm-generic/signal.h
+++ b/libc/kernel/uapi/asm-generic/signal.h
@@ -66,9 +66,9 @@
 #define SIGSYS 31
 #define SIGUNUSED 31
 /* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
-#define SIGRTMIN 32
+#define __SIGRTMIN 32
 #ifndef SIGRTMAX
-#define SIGRTMAX _KERNEL__NSIG
+#define __SIGRTMAX _KERNEL__NSIG
 #endif
 /* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define SA_NOCLDSTOP 0x00000001