Revert "spec: add new language for alias declarations"
Revert "spec: add new language for alias declarations"

This reverts commit aff37662d1f70f2bf9e47b4f962e85521e7c18d1.

Reason: Decision to back out current alias implementation.
https://github.com/golang/go/issues/16339#issuecomment-258527920

Fixes #16339.
Fixes #17746.
Fixes #17784.

Change-Id: I5737b830d7f6fb79cf36f26403b4ad8533ba1dfe
Reviewed-on: https://go-review.googlesource.com/32813
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

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