cmd/compile: switch cannedimports to use a Biobuf
cmd/compile: switch cannedimports to use a Biobuf

Allows eliminating the separate lexer code paths for reading from cp
in the next CL.

Change-Id: I49098ecef32b735c4a01374443c2f847235ff964
Reviewed-on: https://go-review.googlesource.com/19750
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>

theif519/go,binarycrusader/go,goodlang/good,mwhudson/go,CAFxX/go,josharian/go,akutz/go,goodlang/good,codestation/go,ImJasonH/go,goodlang/good,Samurais/go,Cofyc/go,josharian/go,miolini/go,vsekhar/elastic-go,momchil-velikov/go,polyverse-security/go,linux-on-ibm-z/go,cloudflare/go,nawawi/go,nawawi/go,vsekhar/elastic-go,momchil-velikov/go,akutz/go,4ad/go,ganboing/go-esx,polyverse-security/go,theif519/go,linux-on-ibm-z/go,theif519/go,codestation/go,josharian/go,golang/go,theif519/go,golang/go,miolini/go,nawawi/go,vsekhar/elastic-go,ganboing/go-esx,nawawi/go,polyverse-security/go,vsekhar/elastic-go,4ad/go,binarycrusader/go,ganboing/go-esx,codestation/go,akutz/go,cloudflare/go,ImJasonH/go,josharian/go,CAFxX/go,ImJasonH/go,akutz/go,theif519/go,polyverse-security/go,CAFxX/go,momchil-velikov/go,ganboing/go-esx,Cofyc/go,akutz/go,Samurais/go,4ad/go,cloudflare/go,derekmarcotte/go,vsekhar/elastic-go,nawawi/go,4ad/go,Cofyc/go,mwhudson/go,derekmarcotte/go,momchil-velikov/go,Cofyc/go,suncycheng/go,goodlang/good,goodlang/good,codestation/go,momchil-velikov/go,binarycrusader/go,CAFxX/go,golang/go,akutz/go,polyverse-security/go,ganboing/go-esx,vsekhar/elastic-go,suncycheng/go,vsekhar/elastic-go,momchil-velikov/go,mwhudson/go,vanloswang/go,Samurais/go,binarycrusader/go,4ad/go,miolini/go,goodlang/good,nawawi/go,mwhudson/go,vanloswang/go,vanloswang/go,miolini/go,4ad/go,linux-on-ibm-z/go,CAFxX/go,akutz/go,golang/go,derekmarcotte/go,miolini/go,Cofyc/go,nawawi/go,suncycheng/go,Samurais/go,Samurais/go,linux-on-ibm-z/go,ganboing/go-esx,linux-on-ibm-z/go,ganboing/go-esx,theif519/go,vanloswang/go,cloudflare/go,cloudflare/go,codestation/go,vanloswang/go,polyverse-security/go,cloudflare/go,Samurais/go,golang/go,mwhudson/go,ImJasonH/go,miolini/go,nawawi/go,golang/go,ImJasonH/go,linux-on-ibm-z/go,binarycrusader/go,theif519/go,theif519/go,linux-on-ibm-z/go,polyverse-security/go,binarycrusader/go,suncycheng/go,CAFxX/go,josharian/go,vanloswang/go,mwhudson/go,mwhudson/go,golang/go,momchil-velikov/go,derekmarcotte/go,christopher-henderson/Go,linux-on-ibm-z/go,suncycheng/go,derekmarcotte/go,CAFxX/go,4ad/go,josharian/go,ImJasonH/go,goodlang/good,vsekhar/elastic-go,mwhudson/go,codestation/go,momchil-velikov/go,goodlang/good,CAFxX/go,josharian/go,golang/go,binarycrusader/go,miolini/go,suncycheng/go,4ad/go,derekmarcotte/go,polyverse-security/go,Cofyc/go,Cofyc/go,vanloswang/go,ImJasonH/go,Samurais/go,josharian/go,Cofyc/go,ImJasonH/go,suncycheng/go,suncycheng/go,binarycrusader/go,miolini/go,cloudflare/go,derekmarcotte/go,codestation/go,ganboing/go-esx,akutz/go,codestation/go,cloudflare/go,Samurais/go,vanloswang/go,derekmarcotte/go