cleanup: Remove old donut/xl code and erasure implementation.

This is a change to bring in 'klauspost/reedsolomon' library
in #1270 patch.

appveyor.yml

@@ -10,36 +10,20 @@ environment:
   GOPATH: c:\gopath
   GO_EXTLINK_ENABLED: 0
   GO15VENDOREXPERIMENT: 1
-# Remove this after fixing erasure code.
-  GODEBUG: cgocheck=0
 
 # scripts that run after cloning repository
 install:
   - '"C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\SetEnv.cmd" /x64'
-  - curl -fsSL -o c:\go\bin\yasm.exe http://www.tortall.net/projects/yasm/releases/yasm-1.3.0-win64.exe
   - set PATH=%GOPATH%\bin;c:\go\bin;%PATH%
   - rd C:\Go /s /q
   - appveyor DownloadFile https://storage.googleapis.com/golang/go1.6.windows-amd64.zip
   - 7z x go1.6.windows-amd64.zip -oC:\ >nul
-  - curl -fsSL -o mingw-w64.7z http://downloads.sourceforge.net/project/mingw-w64-dgn/mingw-w64/mingw-w64-bin-x86_64-20151206.7z
-  - 7z x -oC:\ mingw-w64.7z > NUL
-  - set PATH=C:\mingw64\bin;%PATH%
-  - x86_64-w64-mingw32-gcc --version
   - go version
   - go env
-  - git clone https://github.com/minio/isa-l
-  - cd isa-l
-  - make -f Makefile.unx arch=mingw
-  - mv include isa-l
-  - set CGO_CPPFLAGS=-Ic:/gopath/src/github.com/minio/minio/isa-l
-  - set CGO_LDFLAGS=c:/gopath/src/github.com/minio/minio/isa-l/isa-l.a
-  - set CC=x86_64-w64-mingw32-gcc
-  - set CXX=x86_64-w64-mingw32-g++
   - cd %GOPATH%\src\github.com\minio\minio
 
 # to run your custom scripts instead of automatic MSBuild
 build_script:
-  - go generate github.com/minio/minio/pkg/crypto/sha1
   - go test .
   - go test -race .
   - go test github.com/minio/minio/pkg...