Function is_non_numeric_identifier_char_or_slash

Returns true if a character is an acceptable (non numeric) identifier char, or '/' An identifier is either a non numeric identifier char, followed by any number of identifier chars, or is a '/' and nothing else. The reason we check if this is *either* a non numeric identifier char, or a '/', is because we will want to use it to parse either 1.a normal identifier 2.'/', 3. something like '/blah'

(ch: char)