Delegate AST node.
EBNF grammar:
delegate-declaration:
(attributes)? (delegate-modifiers)? "delegate" type identifier
(type-parameter-list)? "(" (formal-parameter-list)? ")" (type-parameter-constraints-clauses)? ";"
delegate-modifiers:
(delegate-modifier)+
delegate-modifier:
"new"
"public"
"protected"
"internal"
"private"