merge: trivial fixes

 * insert space to help parsing
 * fix backing global variable for config
 * doxy: fix typos
 * drop dupe prototype
 * lowercase variable
 * doxygen: update docs for #defines
 * add a 'SEC_' prefix to the security flags
 * rename State's members for better legibility
 * rename enum MenuTypes to MenuType
 * convert config dump defines into an enum
 * convert format flags enum into an int
 * tidy mutt_menu_new()