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