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/gdbengine.h

@@ -449,8 +449,9 @@ private: ////////// View & Data Stuff //////////
     QMap<QString, QString> m_varToType;
 
 private: ////////// Dumper Management //////////
-
-    bool startModeAllowsDumpers() const;
+    QString qtDumperLibraryName() const;
+    bool checkDebuggingHelpers();
+    void setDebuggingHelperState(DebuggingHelperState);
     void tryLoadDebuggingHelpers();
     void tryQueryDebuggingHelpers();
     Q_SLOT void recheckDebuggingHelperAvailability();