bytes: add assembly version of Equal for ARM
bytes: add assembly version of Equal for ARM

BenchmarkEqual32                       662          159  -75.98%
BenchmarkEqual4K                     76545        13719  -82.08%
BenchmarkEqual4M                  90136700     23588870  -73.83%
BenchmarkEqual64M               2147483647   1419616000  -42.63%

BenchmarkEqual32                     48.32       201.15    4.16x
BenchmarkEqual4K                     53.51       298.56    5.58x
BenchmarkEqual4M                     46.53       177.81    3.82x
BenchmarkEqual64M                    27.12        47.27    1.74x

R=golang-dev, qyzhai, minux.ma, rsc, iant, nigeltao
CC=golang-dev
http://codereview.appspot.com/6118049

Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,webfd/go-zh,webfd/go-zh,d0f/go-zh,webfd/go-zh,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,Triskite/willstone-goclone,d0f/go-zh,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,webfd/go-zh,webfd/go-zh,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,scirelli/scirelli-go,webfd/go-zh,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,Triskite/willstone-goclone,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,bryanxu/go-zh,rdp/rogerpack2005-golang,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,scirelli/scirelli-go,rdp/rogerpack2005-golang,mhennings/marcohennings-go,scirelli/scirelli-go,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,d0f/go-zh,rdp/rogerpack2005-golang,bryanxu/go-zh,bryanxu/go-zh,bryanxu/go-zh,mhennings/marcohennings-go,d0f/go-zh,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,Triskite/willstone-goclone,mhennings/marcohennings-go,d0f/go-zh,scirelli/scirelli-go,mhennings/marcohennings-go,scirelli/scirelli-go,mhennings/marcohennings-go,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,scirelli/scirelli-go,scirelli/scirelli-go,rdp/rogerpack2005-golang,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang