options::wrapper::headerfunction implementation.
options::callback declaration.
options::wrapper callbacks refactoring.

(void *ptr, size_t size) -> (char *ptr, size_t size).
easy_options refactoring.
options::wrapper::csv_list multi-character separator support.
options::wrapper::bitmask refactoring.
options::wrapper::{enum,long,string}_literal implementation.
options: protocols_all and redir_protocols_all declaration.