compile warnings.

The class definition for SdrMarkView in svx/inc/svx/svdmrkv.hxx
contains two inline methods that take a reference argument and
perform an &rArg == NULL test on it.  The compiler warns that this
condition should always be false because dereferencing a NULL pointer
to generate a reference is not valid in C++ and a valid reference will
never be at address 0.  Warnings are generated every time this header
is included in a .cxx file.

It turns out that there are no callers for the IsGluePoint() method,
so just comment out its definition.

It also turns out that all the callers of IsPointMarked() pass it
a dereferenced pointer, so convert IsPointMarked() to take a pointer
argument and modify all the callers to pass a pointer without
dereferencing it first.