add fs.readstring offset and length
add fs.readstring offset and length

kaustavha/luvit,luvit/luvit,bsn069/luvit,rjeli/luvit,GabrielNicolasAvellaneda/luvit-upstream,GabrielNicolasAvellaneda/luvit-upstream,kaustavha/luvit,GabrielNicolasAvellaneda/luvit-upstream,rjeli/luvit,kaustavha/luvit,zhaozg/luvit,bsn069/luvit,bsn069/luvit,rjeli/luvit,zhaozg/luvit,rjeli/luvit,GabrielNicolasAvellaneda/luvit-upstream,luvit/luvit