Checks that a literal contained in the specified char subarray
is a legal public identifier and returns a string with
the normalized content of the public id.
A group pattern category is a pattern category for group or interleave
patterns whose child patterns are repeatable or not repeatable,
optional or required refs.
A group pattern category is a pattern category for group patterns
whose child patterns are supported by the choice pattern category
or choice patterns whose child patterns are such group patterns.