doc + micro optimization
doc + micro optimization

Optimizations:
- one cmp less in loops (-> do while)
- optimized loops for branch prediction

sunjian1/mysql,VividCortex/mysql,rafaeljusto/mysql,helight/helight_code,aperera/mysql,jockchou/mysql,methane/mysql,beego/mysql,helight/helight_code,VividCortex/mysql,wfxiang08/mysql,helight/helight_code,Go-SQL-Driver/MySQL,Freeaqingme/golang-sql-driver-mysql,netroby/mysql,rlowe/mysql,zhgo/mysql,helight/helight_code,hebihui/mysql,helight/helight_code,joshuaprunier/mysql,LightKool/mysql-go,nanata1115/mysql,yyljlyy/mysql,roth1002/mysql,go-sql-driver/mysql,Vorstack/mysql,henrylee2cn/mysql,helight/helight_code,eXcomm/gomysql,cxflag203/mysql,Frca/mysql,springning/mysql,helight/helight_code,chinanjjohn2012/mysql,dalinaum/go-mysql-driver,bookerzzz/mysql,cw2018/mysql,helight/helight_code,LightKool/mysql-go,segmentio/mysql,hyperworks/mysql,helight/helight_code,muthusubbu459/mysql,bookerzzz/mysql,eklitzke/mysql,yonglehou/mysql,siriele/mysql,tmulchay/mysql,methane/mysql,segmentio/mysql