• fixes #221 - replace codecvt with self-contained UTF-16 conversion
• fixes #218 - add optional limit for number of rows and columns parsed
• fixes #217 - add range checking of unsigned integer type conversions
• document GetColumnIdx and GetRowIdx limitations
• use ptrdiff_t for size comparisons to avoid int truncation
• fix auto-quoting of cells containing carriage return
• fix row label lookup in documents with short rows