286861: Wrong input confuses bash's arithmetic unit permanently

If evalerror (thus longjmp) is called while noeval != 0, it stays nonzero and
assignments cease to work. Such expressions are for example:

let tmp="foo.a"+0   (only in bash 3.2)
let x=(0?(3?4):3)

I think we should reset noeval to zero in the evalexp function (or restore
expr_stack[0], probably).

Written-by: Tomas Janousek <tjanouse@redhat.com>

--- bash-3.2/expr.c.286861	2007-10-23 14:48:38.000000000 +0200
+++ bash-3.2/expr.c	2007-11-06 18:48:24.000000000 +0100
@@ -337,6 +337,7 @@
       return (0);
     }
 
+  noeval = 0;
   val = subexpr (expr);
 
   if (validp)