/*
 * space ::= ' ' | '\t' | '\n' | '\v' | '\f' | '\r'
 * whitespace ::= <space> | <space> <whitespace>
 * optional_space ::= | <space> <optional_space>
 * include_line ::= <optional_space> '#' <optional_space> "include" <optional_space> '<' <filename> '>' <optional_space>
 */