wiki: redirect everything to go.dev/wiki For #61940.
url updates to go.dev / pkg.go.dev
Minor grammar fixes
Minor typo fix
Adding CLI commands for Windows cmd.exe, if PowerShell not available
Updated WindowsCrossCompiling (markdown)
Note about https://github.com/golang/go/issues/24068
add warning about slow builds
Adding a link to GOOS and GOARCH variable docs
Updated page to reflect status with Go 1.5 and newer.
Specify code languages for syntax highlighting
Wiki data import from Google Code