Clear RegexpCache when option saved.
Clear RegexpCache when option saved.

Fixes #1641.

csmalin/vimium,dimatter/vimium,philc/vimium,Robinson10240/vimium,cyrixhero/vimium,borgified/vimium,douglas-larocca/vimium,csmalin/vimium,zhangmin510/vimium,mrmr1993/vimium,borgified/vimium,PrestanceDesign/vimium,bkudria/vimium,wildeyes/vimium,willsALMANJ/vimium,bkudria/vimium,justalittlenoob/vimium,mrmr1993/vimium,borgified/vimium,Robinson10240/vimium,Aleroniponi/vimium,elegantwww/vimium,elegantwww/vimium,poacher2k/vimium,douglas-larocca/vimium,Aleroniponi/vimium,cyrixhero/vimium,VPashkov/vimium,gdh1995/vimium,zhangmin510/vimium,smblott-github/vimium,elegantwww/vimium,VPashkov/vimium,gdh1995/vimium,PrestanceDesign/vimium,Lw-Cui/vimium,dimatter/vimium,philc/vimium,elderbas/vimium,willsALMANJ/vimium,dimatter/vimium,hhsue/vimium,hhsue/vimium,poacher2k/vimium,elderbas/vimium,wildeyes/vimium,hhsue/vimium,Robinson10240/vimium,elderbas/vimium,cyrixhero/vimium,decaffeinate-examples/vimium,zhangmin510/vimium,philc/vimium,PickRelated/vimium,douglas-larocca/vimium,smblott-github/vimium,bkudria/vimium,justalittlenoob/vimium,willsALMANJ/vimium,csmalin/vimium,PrestanceDesign/vimium,wildeyes/vimium,tuchangwei/vimium,tuchangwei/vimium,Lw-Cui/vimium,Lw-Cui/vimium,smblott-github/vimium,poacher2k/vimium,gdh1995/vimium,mrmr1993/vimium,decaffeinate-examples/vimium,tuchangwei/vimium,decaffeinate-examples/vimium,PickRelated/vimium,Aleroniponi/vimium,justalittlenoob/vimium,PickRelated/vimium,VPashkov/vimium