Debugger: Work around wrong executable names

We currently don't always get proper executables from
the process list, and we don't need them for attaching.

Task-number: QTCREATORBUG-11295

Change-Id: I2fc18df0db85063146ed9dc09351844924e22bdc
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Clang: Adjust singleton access style to more recent use.

Change-Id: I7d98f598b1c7f7b871a862ec121b83128d8b2752
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>
Clang: Coding style

Change-Id: Ib7dc759e8db7cf37fbcd7f75d28b29bf95593d6c
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>