Change StereotypesModel member m_stereotypes from pointer to reference:

umbrello/models/stereotypesmodel.h
- Change member m_stereotypes from pointer to reference.
- At constructor change UMLStereotypeList argument from pointer to
  reference.

umbrello/models/stereotypesmodel.cpp
- Adjust code manipulating m_stereotypes to the above change.
- In function addStereotype, if the passed in pointer is not found in
  m_stereotypes then compare the passed in stereotype's name to the
  names in m_stereotypes. If a match is found then do not add the
  pointer passed in.
- In function removeStereotype, if the passed in pointer is not found in
  m_stereotypes then compare the passed in stereotype's name to the
  names in m_stereotypes:
  - If no match is found then return false without attempting removal.
  - If a match is found then remove the matching pointer.

umbrello/umldoc.cpp
- In constructor, on initializing m_stereotypesModel pass m_stereoList
  to constructor of StereotypesModel by reference instead of address.