New vpndrvinst implementation, independent from Cedar and Mayaqua

This greatly improves performance and reduces the binary's size (~0.2 MB vs ~5 MB).

All recent Windows versions are supported, starting with Vista.

No dialogs are created, aside from error/warning ones in case of failure.

The only dependency (aside from Windows libraries) is libhamcore.

src/vpndrvinst/Dialog.c

@@ -0,0 +1,36 @@
+#include "Dialog.h"
+
+#include <stdio.h>
+
+#ifndef WIN32_LEAN_AND_MEAN
+#	define WIN32_LEAN_AND_MEAN
+#endif
+
+#include <windows.h>
+
+int ShowMessage(const char *title, const char *message, const unsigned int type, const va_list args)
+{
+	char buf[MAX_MESSAGE_SIZE];
+	vsnprintf(buf, sizeof(buf), message, args);
+	return MessageBox(NULL, buf, title, type);
+}
+
+int ShowInformation(const char *title, const char *message, ...)
+{
+	va_list args;
+	va_start(args, message);
+	const int ret = ShowMessage(title, message, MB_OK | MB_ICONINFORMATION, args);
+	va_end(args);
+
+	return ret;
+}
+
+int ShowWarning(const char *title, const char *message, ...)
+{
+	va_list args;
+	va_start(args, message);
+	const int ret = ShowMessage(title, message, MB_OK | MB_ICONWARNING, args);
+	va_end(args);
+
+	return ret;
+}