proper handling of signals.
do not run init on g0.

R=r
DELTA=161  (124 added, 23 deleted, 14 changed)
OCL=15490
CL=15497
diff --git a/src/runtime/string.c b/src/runtime/string.c
index 099d7aa..27a7581 100644
--- a/src/runtime/string.c
+++ b/src/runtime/string.c
@@ -53,7 +53,7 @@
 	prints(">");
 	sys·printint(c);
 	prints("\n");
-	throw("bounds");
+	throw("string bounds");
 }
 
 uint32