Fix debugging of terminal applications on Linux

On modern linux distributions (Ubuntu >= 10.10, Debian >= Wheezy),
trying to debug a terminal application fails, with
"ptrace: Operation not permitted".

In order to allow the debugger to attach to the created process, the
process itself needs to inform the kernel of the debugging process.

Task-number: QTCREATORBUG-3509
Change-Id: I68670426fad18cbe3b7cce9d57633e58e631e025
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: hjk <hjk121@nokiamail.com>