CppTools: Fix nextToSurroundingDefinitions

Now it is checked if the adjacent declaration is also defined and one
can define the destination file.

Change-Id: Ifff59c49fc2ab3e2f36f41df42ae4b7d7ff8dd35
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>
CppEditor: Same insert position for quick fixes

Now definitions are inserted at the same position inside the
implementation file for MoveFuncDefOutside and InsertDefFromDecl.

Task-number: QTCREATORBUG-9389
Change-Id: If823ffd15ec39a7bc2edb53519380cb9cabb4c55
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>