Support WASM Architecture

So Go now Supports targeting WASM, but with certain limitations (like not having 'normal' syscalls). It's very low priority and probably a bit of work, but would be a nice 'benchmark' of portability.

First step would be to make the thing compile at all, currently stack of errors I get is down to:

# gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:23:14: undefined: haveArmSha
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:27:16: undefined: cpuid
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:32:13: undefined: xgetbv
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:40:18: undefined: cpuid
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:44:19: undefined: cpuidex
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:52:18: undefined: cpuid
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:56:17: undefined: cpuid
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:61:14: undefined: xgetbv
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:62:20: undefined: cpuidex
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:90:16: undefined: cpuid
../../../gx/ipfs/QmXTpwq2AkzQsPjKqFQDNY2bMdsAT53hUBETeyj8QRHTZU/sha256-simd/cpuid.go:90:16: too many errors
# gx/ipfs/QmPtj12fdwuAqj9sBSTNUxBNu8kCGNp8b3o8yUzMm5GHpq/pb
../../../gx/ipfs/QmPtj12fdwuAqj9sBSTNUxBNu8kCGNp8b3o8yUzMm5GHpq/pb/pb.go:421:9: undefined: terminalWidth
../../../gx/ipfs/QmPtj12fdwuAqj9sBSTNUxBNu8kCGNp8b3o8yUzMm5GHpq/pb/pb.go:430:18: undefined: terminalWidth
# gx/ipfs/QmSvfeW68LC13nVt3BiwHKFneSa4DCdq3erG8RNtJvq7Ni/go-reuseport
../../../gx/ipfs/QmSvfeW68LC13nVt3BiwHKFneSa4DCdq3erG8RNtJvq7Ni/go-reuseport/interface.go:33:9: undefined: available
../../../gx/ipfs/QmSvfeW68LC13nVt3BiwHKFneSa4DCdq3erG8RNtJvq7Ni/go-reuseport/interface.go:50:6: undefined: available
../../../gx/ipfs/QmSvfeW68LC13nVt3BiwHKFneSa4DCdq3erG8RNtJvq7Ni/go-reuseport/interface.go:54:9: undefined: listenStream
../../../gx/ipfs/QmSvfeW68LC13nVt3BiwHKFneSa4DCdq3erG8RNtJvq7Ni/go-reuseport/interface.go:61:6: undefined: available
../../../gx/ipfs/QmSvfeW68LC13nVt3BiwHKFneSa4DCdq3erG8RNtJvq7Ni/go-reuseport/interface.go:65:9: undefined: listenPacket
../../../gx/ipfs/QmSvfeW68LC13nVt3BiwHKFneSa4DCdq3erG8RNtJvq7Ni/go-reuseport/interface.go:72:6: undefined: available
../../../gx/ipfs/QmSvfeW68LC13nVt3BiwHKFneSa4DCdq3erG8RNtJvq7Ni/go-reuseport/interface.go:102:6: undefined: available
../../../gx/ipfs/QmSvfeW68LC13nVt3BiwHKFneSa4DCdq3erG8RNtJvq7Ni/go-reuseport/interface.go:106:9: undefined: dial

Built with GOOS=js GOARCH=wasm go build -tags="nofuse purego" -ldflags="-X "github.com/ipfs/go-ipfs".CurrentCommit=47e9466ac" -o "cmd/ipfs/ipfs" "github.com/ipfs/go-ipfs/cmd/ipfs"

• sha256-simd - fixed in https://github.com/minio/sha256-simd/pull/33, so an update will fix those
• go-reuseport - we should find a way to just disable it, probably by either just plugin-ifying transports or sprinkling build tags injecting dummy things in place of the implementation. Probably a good excuse to fix some technical debt.
• pb (progress bar) - no idea, probably just PR a fix/workaround

Next step would be to write some transport to talk to outside nodes. /ws//wss should be easy to wrap.