[DRAFT][PATCH] org-encode-time compatibility and convenience helper

[Max Nikulin]

Hi,

After a recent report of incorrect daylight saving time handling in agenda:

Ignacio Casso [BUG] org-agenda thinks timestamps after 23:00 correspond 
to the next day Tue, 29 Mar 2022 15:09:10 +0200
https://list.orgmode.org/PAXPR06MB7760238F410CBE3203F78EE0C61E9@PAXPR06MB7760.eurprd06.prod.outlook.com

I tried to create a compatibility helper that will use currently 
recommended way to call `encode-time' with single list argument for 
Emacs-27 and newer, but use the only available call style as separated 
arguments for older Emacs versions.

From my point of view
- it should work at the compile or load time to minimize runtime 
performance impact,
- since both ways to call `encode-time' are necessary (in a half of 
cases a list returned by `decode-time' is available, in other cases 
timestamps are assembled from scratch, none is preferred), it should be 
convenient in both cases,
- it should allow Org to work even if support of multiple `encode-time' 
arguments will be removed from Emacs.

Paul Eggert proposed org-encode-time-1 defsubst/defun
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=54764#10

My patch requires more changes since the macro is just defined but not 
actually used. It does not fix the problem with "no DST" flag returned 
by some function in Org. I can prepare next patches, but I think it 
should be decided at first which approach should be accepted by Org Mode:
- org-encode-time accepting both list or separate arguments
- mix of `encode-time' with multiple arguments and org-encode-time-1 for 
lists.

0001-org-macs.el-Introduce-a-helper-for-encode-time.patch
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