editors/mg: Update 20241008 => 20260519

Changelog:

• file.c: improve the "No changes need to be saved" check
• fileio.c, funmap.c, echo.c: handle strdup failure
• re_search.c: fix regex-replace infinite loop issues
• word.c: rework grabword() a bit; plug a memory leak
• interpreter.c: fix two memory leaks
• dired.c: improve externs for KEYMAPE()
• mg.1: fix typo

https://cvsweb.openbsd.org/src/usr.bin/mg/

PR: 295474
MFH: 2026Q2
Approved by: osa, vvd (Mentors, implicit)