unicode/utf16: add benchmarks
unicode/utf16: add benchmarks

For #6957

Change-Id: Ic497c12f33efc933e9fe81f6cd1b2a0a01abbabf
Reviewed-on: https://go-review.googlesource.com/19820
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

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