添加注释，为解决部分表格中文读取乱码做准备

Author: chen.s.g

Diff for: workbook.go

@@ -80,16 +80,16 @@ func (wb *WorkBook) parseBof(buf io.ReadSeeker, b *bof, pre *bof, offset_pre int
 		binary.Read(item, binary.LittleEndian, &wb.Codepage)
 	case 0x003c: // SST CONTINUE identifier
 		if pre.Id == 0x00fc {
-			var size uint16
 			var err error
+			var str string
+			var size uint16
 			if wb.continue_utf16 >= 1 {
 				size = wb.continue_utf16
 				wb.continue_utf16 = 0
 			} else {
 				err = binary.Read(item, binary.LittleEndian, &size)
 			}
 			for err == nil && offset_pre < len(wb.sst) {
-				var str string
 				if size > 0 {
 					str, err = wb.parseString(item, size)
 					wb.sst[offset_pre] = wb.sst[offset_pre] + str
@@ -215,23 +215,23 @@ func (w *WorkBook) parseString(buf io.ReadSeeker, size uint16) (res string, err
 		var flag byte
 		err = binary.Read(buf, binary.LittleEndian, &flag)
 
-		// Rich-Text settings (richtext)
+		// Rich-Text settings (richtext), 0 = Does not contain Rich-Text settings, 1 = Contains Rich-Text settings
 		if flag&0x8 != 0 {
 			err = binary.Read(buf, binary.LittleEndian, &richtext_num)
 		} else if w.continue_rich > 0 {
 			richtext_num = w.continue_rich
 			w.continue_rich = 0
 		}
 
-		// Asian phonetic settings
+		// Asian phonetic settings, 0 = Does not contain Asian phonetic settings, 1 = Contains Asian phonetic settings
 		if flag&0x4 != 0 {
 			err = binary.Read(buf, binary.LittleEndian, &phonetic_size)
 		} else if w.continue_apsb > 0 {
 			phonetic_size = w.continue_apsb
 			w.continue_apsb = 0
 		}
 
-		// Character compression
+		// Character compression, 0 = Compressed (8-bit characters), 1 = Uncompressed (16-bit characters)
 		if flag&0x1 != 0 {
 			var bts = make([]uint16, size)
 			var i = uint16(0)