Debugger: Handle failing inferior calls more gracefully

At least for GDB on Windows that's a rather typical situation due to
GDB's "Internal error: pc in read in psymtab, but not in symtab"

Task-number: QTCREATORBUG-11164

Change-Id: If79d586b59e2c1ee37558e8a811091fefc69ac2d
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Debugger: Robustify QSet and QHash dumpers

Change-Id: I6d4df7f00719e5f7c4ee2f41c890348ab9aeaa8a
Reviewed-by: Christian Stenger <christian.stenger@digia.com>