potential fixes for debian time_t transition

[elliefm]

This draft PR is for producing patches so that @guimard can check for whether they fix #4876 or not.

[dilyanpalauzov]

https://wiki.debian.org/ReleaseGoals/64bit-time contains:

Dpkg enabling -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64
Because you have to have LFS if you have 64-bit time_t (glibc enforces this), this goal is a superset of ReleaseGoals/LFS

The latter includes

For projects using autoconf, by adding the AC_SYS_LARGEFILE m4 macro.

This likely means, that Debian compiles with -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64, and irrespective of this AC_SYS_LARGEFILE must be called. But autoconf definition of AC_SYS_LARGEFILE also states “Define ‘_FILE_OFFSET_BITS’ and ‘_LARGE_FILES’ if necessary.” - I do not know if this is necessary.

All that said, I think adjusting to time_t means calling explicitly AC_SYS_LARGEFILE, which is currently not done.

[elliefm]

This is now #5009