SConstruct has mixed tabs and spaces

[habamax]

line 60 indented with spaces:

if (os.name=="posix"):
    pass
elif (os.name=="nt"):
    if (os.getenv("VSINSTALLDIR")==None): # <------------------ HERE
    custom_tools=['mingw']

[antarktikali]

In general there are some extra whitespaces and indentation errors in some cpp files. Maybe we should clean them up...

[akien-mga]

I'll check if this is still valid nowadays, and if so propose a small PR.