Streamline usage of error code types and error handling itself

[mback2k]

At the moment various types of error handling code flows and error code types are used, e.g.:

• HRESULT
• LSTATUS
• Win32 error code
• Boolean

[mback2k]

Analysis of current type usage:

• wiasane => HRESULT
• strutil => HRESULT, LONG, BOOL
• winsane => HRESULT, LONG, BOOL, SANEStatus, SANE*
• devsane => DWORD
• coisane => DWORD, BOOL