[PATCH] uml: block SIGWINCH in ptrace tester child

The process that UML uses to probe the host's ptrace capabilities can (rarely)
receive a SIGWINCH, confusing the parent.  This fixes that by blocking
SIGWINCH.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>