[http] Allow for domain names within NTLM user names

Allow a NetBIOS domain name to be specified within a URL using a
syntax such as:

  http://domain%5Cusername:password@server/path

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/netbios.h

@@ -0,0 +1,30 @@
+#ifndef _IPXE_NETBIOS_H
+#define _IPXE_NETBIOS_H
+
+/** @file
+ *
+ * NetBIOS user names
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+extern const char * netbios_domain ( char **username );
+
+/**
+ * Restore NetBIOS [domain\]username
+ *
+ * @v domain		NetBIOS domain name
+ * @v username		NetBIOS user name
+ *
+ * Restore the separator in a NetBIOS [domain\]username as split by
+ * netbios_domain().
+ */
+static inline void netbios_domain_undo ( const char *domain, char *username ) {
+
+	/* Restore separator, if applicable */
+	if ( domain )
+		username[-1] = '\\';
+}
+
+#endif /* _IPXE_NETBIOS_H */