remove grow case differentiation
remove grow case differentiation

benchmarks:
http://play.golang.org/p/xMWTHiu9JY

https://groups.google.com/forum/?fromgroups=#!topic/golang-nuts/ETbw1ECDgRs

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