Document new flags for AST_TYPE (null/false)

Author: TysonAndre

.travis.yml

@@ -6,7 +6,7 @@ php:
   - 7.1
   - 7.2
   - 7.3
-  - 7.4snapshot
+  - 7.4
   - nightly
 
 before_script:

README.md

@@ -267,6 +267,8 @@ ast\flags\TYPE_DOUBLE
 ast\flags\TYPE_STRING
 ast\flags\TYPE_ITERABLE
 ast\flags\TYPE_OBJECT
+ast\flags\TYPE_NULL   // php 8.0 union types
+ast\flags\TYPE_FALSE  // php 8.0 union types
 
 // Used by ast\AST_CAST (exclusive)
 ast\flags\TYPE_NULL