cppcheck: fix some reports (#6386)
[nvdaHelper/common/ia2utils.cpp:24]: (performance) Prefer prefix ++/-- operators for non-primitive types.
[nvdaHelper/local/dllImportTableHooks.cpp:102]: (performance) Prefer prefix ++/-- operators for non-primitive types.
[nvdaHelper/remote/displayModel.cpp:290]: (error) Mismatching allocation and deallocation: srcFocusRect
