runtime: use conventional shift style for gcBitsChunkBytes
runtime: use conventional shift style for gcBitsChunkBytes

The convention for writing something like "64 kB" is 64<<10, since
this is easier to read than 1<<16. Update gcBitsChunkBytes to follow
this convention.

Change-Id: I5b5a3f726dcf482051ba5b1814db247ff3b8bb2f
Reviewed-on: https://go-review.googlesource.com/23132
Reviewed-by: Rick Hudson <838bd060584c511f21c75c69ea04b7b120d86af0@golang.org>

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