Fix 'when' keyword parsing to respect 'use feature switch'

[fglock]

Problem

The when keyword was being treated as a reserved keyword unconditionally, causing parser errors when used as a bareword hash key. This broke ExifTool's XMP.pm which uses when as a hash key:

when => { %dateTimeInfo, Groups => { 2 => 'Time' } }

The when keyword should only be reserved when use feature 'switch' is active, similar to how try and class are handled.

Changes

StatementResolver.java

• Added feature flag checks for given, when, and default keywords
• These keywords now only act as statement keywords when use feature 'switch' is enabled
• Without the feature, they fall through to be treated as regular identifiers

ListParser.java (2 locations)

• Added when to the list of keywords that should be treated as barewords when followed by => (fat comma)
• This matches the existing behavior for and, or, and xor keywords

Testing

Tested with ExifTool 13.44:

Before fix:

Expected token OPERATOR with text ) but got LexerToken{type=IDENTIFIER, text='when'}

After fix:

• XMP.pm parses successfully
• Commands like -h, -json, -X, -listx now proceed past the parser stage
• The when => { ... } hash key is correctly recognized as a bareword

Impact

This fix allows code that uses when as a bareword (hash keys, subroutine names, etc.) to work correctly when the switch feature is not enabled, matching standard Perl behavior.