Windows: utilize ShellExecuteW

On Windows, use the `ShellExecuteW` syscall instead of an external command. The
`HideWindow` option is no longer configurable, as `setFlags` assumes an external
command is to be run. Long term, would be better to refactor the package, as
different Window behavior can be configured via the last argument to
`ShellExecuteW` (`nShowCmd`).

https://docs.microsoft.com/windows/win32/api/shellapi/nf-shellapi-shellexecutew

Fixes pkg#16

Author: Steven Penny

browser_windows.go

@@ -1,16 +1,13 @@
+//go:generate mkwinsyscall -output zbrowser_windows.go browser_windows.go
+//sys ShellExecute(hwnd int, verb string, file string, args string, cwd string, showCmd int) (err error) = shell32.ShellExecuteW
 package browser
 
-import (
-	"os/exec"
-	"strings"
-	"syscall"
-)
+import "os/exec"
+const SW_SHOWNORMAL = 1
 
 func openBrowser(url string) error {
-	r := strings.NewReplacer("&", "^&")
-	return runCmd("cmd", "/c", "start", r.Replace(url))
+   return ShellExecute(0, "", url, "", "", SW_SHOWNORMAL)
 }
 
 func setFlags(cmd *exec.Cmd) {
-	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
 }