Debugger: Initial implementation of conditional breakpoints

Expression class to store compiled expressions and associated variable list.

Co-authored-by:  TryTwo <taolas@gmail.com>

Source/Core/DolphinQt/Debugger/NewBreakpointDialog.h

@@ -34,6 +34,7 @@ private:
   QRadioButton* m_instruction_bp;
   QGroupBox* m_instruction_box;
   QLineEdit* m_instruction_address;
+  QLineEdit* m_instruction_condition;
 
   // Memory BPs
   QRadioButton* m_memory_bp;