[uri] Support "file:" URIs describing relative paths

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

src/core/uri.c

 		 * the reparsing of the URI, allowing everything else
 		 * (e.g. ':', which will appear in iSCSI URIs).
 		 */
-		[URI_OPAQUE]	= "/#",
+		[URI_OPAQUE]	= "#",
 		/* User name: escape everything */
 		[URI_USER]	= "/#:@?",
 		/* Password: escape everything */

src/tests/uri_test.c

 
 /** File URI with relative (opaque) path */
 static struct uri_test uri_file_relative = {
-	"file:script.ipxe",
+	"file:boot/script.ipxe",
 	{
 		.scheme = "file",
-		.opaque = "script.ipxe",
+		.opaque = "boot/script.ipxe",
 	},
 };