Provide default index names for SQLite

The allegedly default names were never used causing the first index
created without a name to fail and subsequent indices to be named 02,
03, 04...  This uses the table name with '_idx' appended as the default,
similar to the PostgreSQL producer.

lib/SQL/Translator/Producer/SQLite.pm

@@ -225,15 +225,13 @@ sub create_table
     #
     # Indices
     #
-    my $idx_name_default = 'A';
     for my $index ( $table->get_indices ) {
         push @index_defs, create_index($index);
     }
 
     #
     # Constraints
     #
-    my $c_name_default = 'A';
     for my $c ( $table->get_constraints ) {
         if ($c->type eq "FOREIGN KEY") {
             push @field_defs, create_foreignkey($c);
@@ -283,14 +281,13 @@ sub create_index
 {
     my ($index, $options) = @_;
 
-    my $name   = $index->name;
-    $name      = mk_name($name);
+    (my $index_table_name = $index->table->name) =~ s/^.+?\.//; # table name may not specify schema
+    my $name   = mk_name($index->name || "${index_table_name}_idx");
 
     my $type   = $index->type eq 'UNIQUE' ? "UNIQUE " : '';
 
     # strip any field size qualifiers as SQLite doesn't like these
     my @fields = map { s/\(\d+\)$//; _generator()->quote($_) } $index->fields;
-    (my $index_table_name = $index->table->name) =~ s/^.+?\.//; # table name may not specify schema
     $index_table_name = _generator()->quote($index_table_name);
     warn "removing schema name from '" . $index->table->name . "' to make '$index_table_name'\n" if $WARN;
     my $index_def =
@@ -304,10 +301,9 @@ sub create_constraint
 {
     my ($c, $options) = @_;
 
-    my $name   = $c->name;
-    $name      = mk_name($name);
-    my @fields = map _generator()->quote($_), $c->fields;
     (my $index_table_name = $c->table->name) =~ s/^.+?\.//; # table name may not specify schema
+    my $name   = mk_name($c->name || "${index_table_name}_idx");
+    my @fields = map _generator()->quote($_), $c->fields;
     $index_table_name = _generator()->quote($index_table_name);
     warn "removing schema name from '" . $c->table->name . "' to make '$index_table_name'\n" if $WARN;