CodeAssist: Move base position to interface.

Every proposal needs to have a base postion.
Move it to the base class to reduce duplicated code.

Change-Id: I0b1b8282dfe955d251646661f755bf9f585fbad1
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/texteditor/codeassist/functionhintproposal.cpp

@@ -30,7 +30,7 @@
 using namespace TextEditor;
 
 FunctionHintProposal::FunctionHintProposal(int cursorPos, IFunctionHintProposalModel *model)
-    : m_basePosition(cursorPos)
+    : IAssistProposal(cursorPos)
     , m_model(model)
 {}
 
@@ -42,11 +42,6 @@ bool FunctionHintProposal::isFragile() const
     return true;
 }
 
-int FunctionHintProposal::basePosition() const
-{
-    return m_basePosition;
-}
-
 bool FunctionHintProposal::isCorrective() const
 {
     return false;