9.1.0: XP 11 compatibility

• Made compatible with XP 11, see xp-framework/core#300 - @thekid

9.0.0: Drop PHP 5 support

• Implemented xp-framework/rfc#334: Drop PHP 5.6:
  . Heads up: Minimum required PHP version now is PHP 7.0.0
  . Rewrote code base, grouping use statements
  . Rewrote isset(X) ? X : default to X ?? default
  . Converted newinstance to anonymous classes
  (@thekid)

8.0.2: Undefined variable fix

• Fix "Undefined variable $cmp" when comparing MatchResult instances
  (@thekid)

8.0.1: XP10 compatibility

• Made compatible with XP 10 - @thekid

8.0.0: XP9 Compatibility

• Heads up: Dropped PHP 5.5 support - @thekid
• Added compatibility with XP 9.0+ - @thekid

7.1.1: PHP 7.2 compatibility

• Added BC for PHP 7.2: Empty optional patterns should not be NULLed
  See https://bugs.php.net/bug.php?id=73947
  (@thekid)

7.1.0: XP8 Compatibility

• Added version compatibility with XP 8 - @thekid

7.0.0: XP7 compatibility

• Adopted semantic versioning. See xp-framework/rfc#300 - @thekid
• Added version compatibility with XP 7 - @thekid

6.6.0: Extract from XP Core

• Extracted from the XP Framework's core - @thekid