SvMemoryStream.remainingSize ret. size to end of data not buffer

SvMemoryStream remainingSize returned the size from current
position to internal buffer size instead to end of data. This
was not consistent with what remainingSize description says on
SvStream (and other SvStream implementations work) and what the
user expects.

Change-Id: I7ff391754a386c5f067a4bd4eed2ee7f2d7fd77e

include/tools/stream.hxx

@@ -736,7 +736,7 @@ public:
     bool            IsObjectMemoryOwner() { return bOwnsData; }
     void            SetResizeOffset( sal_Size nNewResize ) { nResize = nNewResize; }
     sal_Size        GetResizeOffset() const { return nResize; }
-    virtual sal_uInt64 remainingSize() SAL_OVERRIDE { return GetBufSize() - Tell(); }
+    virtual sal_uInt64 remainingSize() SAL_OVERRIDE { return GetEndOfData() - Tell(); }
 };
 
 class TOOLS_DLLPUBLIC SvScriptStream: public SvStream