go: include vendored modules

RHEL requires the source code for dependencies to be included in the
srpm. The spec file already expects that, but we've only included the
vendored modules (i.e., the `vendor` directory) in the `rhel-8.2.`
branch. Move vendoring to master, so that we can build RHEL packages
from it as well.

This commit is the result of running `go mod vendor`, which includes the
vendored sources and updates go.mod and go.sum files.

Fedora requires the opposite: dependencies should not be vendored. The
spec file already ignores the `vendor` directory by default.

vendor/github.com/mattn/go-ieproxy/ieproxy.go

@@ -0,0 +1,51 @@
+// Package ieproxy is a utility to retrieve the proxy parameters (especially of Internet Explorer on windows)
+//
+// On windows, it gathers the parameters from the registry (regedit), while it uses env variable on other platforms
+package ieproxy
+
+import "os"
+
+// ProxyConf gathers the configuration for proxy
+type ProxyConf struct {
+	Static    StaticProxyConf // static configuration
+	Automatic ProxyScriptConf // script configuration
+}
+
+// StaticProxyConf contains the configuration for static proxy
+type StaticProxyConf struct {
+	// Is the proxy active?
+	Active bool
+	// Proxy address for each scheme (http, https)
+	// "" (empty string) is the fallback proxy
+	Protocols map[string]string
+	// Addresses not to be browsed via the proxy (comma-separated, linux-like)
+	NoProxy string
+}
+
+// ProxyScriptConf contains the configuration for automatic proxy
+type ProxyScriptConf struct {
+	// Is the proxy active?
+	Active bool
+	// PreConfiguredURL of the .pac file.
+	// If this is empty and Active is true, auto-configuration should be assumed.
+	PreConfiguredURL string
+}
+
+// GetConf retrieves the proxy configuration from the Windows Regedit
+func GetConf() ProxyConf {
+	return getConf()
+}
+
+// OverrideEnvWithStaticProxy writes new values to the
+// `http_proxy`, `https_proxy` and `no_proxy` environment variables.
+// The values are taken from the Windows Regedit (should be called in `init()` function - see example)
+func OverrideEnvWithStaticProxy() {
+	overrideEnvWithStaticProxy(GetConf(), os.Setenv)
+}
+
+// FindProxyForURL computes the proxy for a given URL according to the pac file
+func (psc *ProxyScriptConf) FindProxyForURL(URL string) string {
+	return psc.findProxyForURL(URL)
+}
+
+type envSetter func(string, string) error