Fix ExecCommandWith for cmd.exe in Windows

Close 1018

Run the command as is in cmd.exe with no parsing and escaping.
Explicity set cmd.SysProcAttr so execCommand does not escape the command.
Technically, the command should be escaped with ^ for special characters, including ".
This allows cmd.exe commands to be chained together.

See neovim/neovim#7343 (comment)

However, this requires a new shellescape function that is specific to one of the following:
- interactive prompt
- batchfile
- command name
fzf#shellescape in the Vim plugin can handle only the batchfile.

src/util/util_windows.go

@@ -6,8 +6,6 @@ import (
 	"os"
 	"os/exec"
 	"syscall"
-
-	"github.com/mattn/go-shellwords"
 )
 
 // ExecCommand executes the given command with cmd
@@ -18,11 +16,13 @@ func ExecCommand(command string) *exec.Cmd {
 // ExecCommandWith executes the given command with cmd. _shell parameter is
 // ignored on Windows.
 func ExecCommandWith(_shell string, command string) *exec.Cmd {
-	args, _ := shellwords.Parse(command)
-	allArgs := make([]string, len(args)+1)
-	allArgs[0] = "/c"
-	copy(allArgs[1:], args)
-	return exec.Command("cmd", allArgs...)
+	cmd := exec.Command("cmd")
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+	    HideWindow: false,
+	    CmdLine: fmt.Sprintf(` /s /c "%s"`, command),
+	    CreationFlags: 0,
+	}
+	return cmd
 }
 
 // IsWindows returns true on Windows