cmd/compile: avoid one symbol lookup for qualified identifiers
cmd/compile: avoid one symbol lookup for qualified identifiers

For -newparser only.

Change-Id: I0eaa05035df11734e2bda7ad456b9b30485d9465
Reviewed-on: https://go-review.googlesource.com/31718
Reviewed-by: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>

linux-on-ibm-z/go,cloudflare/go,linux-on-ibm-z/go,goodlang/good,codestation/go,suncycheng/go,linux-on-ibm-z/go,derekmarcotte/go,goodlang/good,CAFxX/go,vsekhar/elastic-go,linux-on-ibm-z/go,golang/go,vsekhar/elastic-go,linux-on-ibm-z/go,goodlang/good,linux-on-ibm-z/go,nawawi/go,golang/go,Cofyc/go,ImJasonH/go,josharian/go,derekmarcotte/go,polyverse-security/go,josharian/go,derekmarcotte/go,josharian/go,josharian/go,ImJasonH/go,CAFxX/go,linux-on-ibm-z/go,vsekhar/elastic-go,nawawi/go,codestation/go,golang/go,polyverse-security/go,derekmarcotte/go,ImJasonH/go,Cofyc/go,cloudflare/go,akutz/go,polyverse-security/go,Cofyc/go,suncycheng/go,linux-on-ibm-z/go,derekmarcotte/go,goodlang/good,suncycheng/go,nawawi/go,CAFxX/go,vsekhar/elastic-go,akutz/go,nawawi/go,derekmarcotte/go,golang/go,josharian/go,akutz/go,Cofyc/go,akutz/go,akutz/go,polyverse-security/go,cloudflare/go,cloudflare/go,golang/go,josharian/go,cloudflare/go,suncycheng/go,nawawi/go,suncycheng/go,suncycheng/go,cloudflare/go,CAFxX/go,golang/go,CAFxX/go,codestation/go,ImJasonH/go,codestation/go,vsekhar/elastic-go,polyverse-security/go,akutz/go,polyverse-security/go,nawawi/go,derekmarcotte/go,codestation/go,akutz/go,cloudflare/go,nawawi/go,goodlang/good,josharian/go,ImJasonH/go,josharian/go,Cofyc/go,CAFxX/go,cloudflare/go,nawawi/go,Cofyc/go,christopher-henderson/Go,ImJasonH/go,polyverse-security/go,vsekhar/elastic-go,ImJasonH/go,ImJasonH/go,CAFxX/go,goodlang/good,vsekhar/elastic-go,codestation/go,suncycheng/go,CAFxX/go,codestation/go,goodlang/good,codestation/go,polyverse-security/go,akutz/go,golang/go,Cofyc/go,suncycheng/go,vsekhar/elastic-go,goodlang/good,golang/go,Cofyc/go,derekmarcotte/go