Enum AST node.
EBNF grammar:
enum-declaration:
(attributes)? (enum-modifiers)? "enum" identifier
(enum-base)? enum-body (";")?
enum-base:
":" integral-type
enum-body:
"{" (enum-member-declarations)? "}"
"{" enum-member-declarations "," "}"
enum-modifiers:
(enum-modifier)+
enum-modifier:
"new"
"public"
"protected"
"internal"
"private"
enum-member-declarations:
enum-member-declaration ( "," enum-member-declaration )*