Fix grammar compression regression causing array index gaps

The grammar expansion code caused duplicit entries for expanded rules
that are used in multiple different entries. When creating an index of the
grammar rules, this caused array index gaps, converting a list array to an
associative array with indexes included in the compressed grammar.

Author: JanJakes

grammar-tools/convert-grammar.php

@@ -165,17 +165,17 @@ function expand( $value ) {
 	$last = $value[ strlen( $value ) - 1 ];
 	$name = substr( $value, 0, -1 );
 	if ( '?' === $last ) {
-		$expanded[] = array(
+		$expanded[ $value ] = array(
 			'name'  => $value,
 			'value' => array( array( $name ), array( 'ε' ) ),
 		);
 	} elseif ( '*' === $last ) {
-		$expanded[] = array(
+		$expanded[ $value ] = array(
 			'name'  => $value,
 			'value' => array( array( $name, $value ), array( $name ), array( 'ε' ) ),
 		);
 	} elseif ( '+' === $last ) {
-		$expanded[] = array(
+		$expanded[ $value ] = array(
 			'name'  => $value,
 			'value' => array( array( $name, $value ), array( $name ) ),
 		);