Type Conversion Error for Qt5.7

[Mini4Ever]

As I am in need of creating .slx files for Matlab, your library could give me a good head start. However, when compiling for Qt5.7, I got an error for line 40 of smlworkbook.cpp where there is an incompatible return type for Workbook::bookView given the return expression. For now, I have avoided the error by removing the .toInt() call in the return expression, but I have no clue whether this makes any sense.

Look forward to a proper fix.

PS.: I also got a few warnings on unused parameters and other things like calling deprecated functions.