Debugger: Use LD_PRELOAD to load debugging helper.

on UNIX. Either set the LD_PRELOAD environment variable
using a gdb command or have the TermGdbAdapter set the
variable for the debuggee. For the remote adapter,
switch on toolchain. dlopen() is a fallback for
platforms where it is not supported and attaching
to running processes. Fixes a crash with gdb 7.0
(and spurious gdb 6.8 crashes with dlopen()).
Reviewed-by: hjk <qtc-committer@nokia.com>

src/plugins/debugger/gdb/abstractgdbadapter.h

@@ -48,6 +48,11 @@ class AbstractGdbAdapter : public QObject
     Q_OBJECT
 
 public:
+    enum  DumperHandling { DumperNotAvailable,
+                           DumperLoadedByAdapter,
+                           DumperLoadedByGdbPreload,
+                           DumperLoadedByGdb };
+
     AbstractGdbAdapter(GdbEngine *engine, QObject *parent = 0);
     virtual ~AbstractGdbAdapter();
 
@@ -61,7 +66,7 @@ public:
     virtual void shutdown();
     virtual const char *inferiorShutdownCommand() const;
 
-    virtual bool dumpersAvailable() const = 0;
+    virtual DumperHandling dumperHandling() const = 0;
 
     static QString msgGdbStopFailed(const QString &why);
     static QString msgInferiorStopFailed(const QString &why);