fix PR3965:SIGINT handler not restored after calling ParseAST(),
patch by Alexei Svitkine!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68929 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/System/Unix/Signals.inc b/lib/System/Unix/Signals.inc
index be22bd8..e385e0c 100644
--- a/lib/System/Unix/Signals.inc
+++ b/lib/System/Unix/Signals.inc
@@ -126,7 +126,8 @@
       IF();        // run the interrupt function.
       return;
     }
-    exit(1);   // If this is an interrupt signal, exit the program
+    raise(Sig);   // Execute the default handler.
+    return;
   }
 
   // Otherwise if it is a fault (like SEGV) run any handler.