relnotes: add notes for 6.1.1
This also fixes the header for 6.1 from 6.1rc0
from__future__importabsolute_importfrommercurial.i18nimport_frommercurialimportchangegroup,error,extensionsdefabort(orig,*args,**kwargs):raiseerror.Abort(_('this is an exercise'))defuisetup(ui):extensions.wrapfunction(changegroup,'getbundler',abort)