5.4.1: PHP 8.0.0RC1 compatibility

• Fixed #90: Namespace declaration statement has to be the very first
  statement, which occured with PHP 8.0.0RC1
  (@thekid)

5.4.0: RFC 336

• Implemented second step for #86: Add an E_DEPRECATED warning to the
  hacklang annotation syntax <<...>>; details in xp-framework/ast#9
  (@thekid)
• Merged PR #89: Add annotation type mappings to TARGET_ANNO detail
  (@thekid)
• Changed PHP 8 attributes to be emitted in XP meta information without
  namespaces, and with their first characters lowercased. This way, code
  using annotations will continue to work, see xp-framework/rfc#336.
  (@thekid)

5.3.0: Named arguments for PHP 8

• Merged PR #88: Emit named arguments for PHP 8 - @thekid

5.2.1: AST library forward compatibility

• Adjusted to xp-framework/ast yielding comments as-is, transform
  them to the form XP meta information expects.
  (@thekid)

5.2.0: PHP 8 attributes, match and nullsafe operator

• Merged PR #87: Add support for match expression - @thekid
• Implemented first step of #86: Support PHP 8 attributes - @thekid
• Removed lang.ast.syntax.php.NullSafe in favor of builtin support
  (@thekid)
• Merged PR #84: Extract parser - @thekid

5.1.3: Allow ::class on objects

• Allowed ::class on objects (PHP 8.0 forward compatibility) - @thekid

5.1.2: Promotion of by-reference parameters fix

• Fixed promotion for by-reference arguments - @thekid

5.1.1: Operator precedence fix

• Fixed ternary and instanceof operators' precedence - @thekid

5.1.0: PHP 8 syntax adoptions

• Merged PR #82: Allow chaining scope resolution operator :: - @thekid
• Merged PR #81: Allow instanceof (<expr>) as syntax - @thekid
• Merged PR #80: Allow new (<expr>) as syntax - @thekid

5.0.0: Drop PHP5

• Merged PR #70: Extract compact methods; to use these, require the
  library https://github.com/xp-lang/php-compact-methods
  (@thekid)
• Merged PR #79: Convert testsuite to baseless tests - @thekid
• Merged PR #78: Deprecate curly brace syntax for offsets; consistent
  with PHP 7.4
  (@thekid)
• Added support for XP 10 and newer versions of library dependencies
  (@thekid)
• Implemented xp-framework/rfc#334: Drop PHP 5.6. The minimum required
  PHP version is now 7.0.0!
  (@thekid)