Increase the size of the alternate stack. It was too small.

This was found by accident and there is no known way to detect
an overflow of an alternate stack in the general case.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15018 a5019735-40e9-0310-863c-91ae7b9d1cf9

Author: florian

memcheck/tests/sigaltstack.c

@@ -14,7 +14,7 @@ int main(int argv, char** argc) {
   int res, i;
   stack_t sigstk;
   struct sigaction act;
-  static const int size = SIGSTKSZ*2;
+  static const int size = SIGSTKSZ*4;
   // We give EXEC permissions because this won't work on ppc32 unless you
   // ask for an alt stack with EXEC permissions,
   // since signal returning requires execution of code on the stack.