CVE-2022-2257: fix out-of-bounds read in str2special() when advancing
past the trailing NUL of a menu item with only a modifier (message.c,
upstream patch 9.0.0009)
CVE-2022-2182: fix heap buffer overflow in parse_cmd_address() when
address line 0 is used with the ";" separator (":0;/PATTERN/"); clamp
cursor column via check_cursor_col() for line 0 (ex_docmd.c, upstream
patch 8.2.5150)
CVE-2022-2849: return zero byte length for NUL in latin_ptr2len() and
dbcs_ptr2len() so iterating past the end of a null string cannot
dereference an invalid address (mbyte.c, upstream patch 9.0.0220;
minimal form — only the functional changes backported)