bug#56241: [PATCH] icalendar doesn't correctly process arbitrary diary sexp entries

[hokomo]

> Right; I can reproduce that problem.  I've added Ulf to the CCs; perhaps
> he has some comments.

It's been a week since then. Any ideas on how to move forward or should 
we give it more time? :-)

To summarize, the problems are:

(1) A diary sexp not generating any events for the configured number of 
enumeration days is treated effectively as a parsing failure, meaning 
that the next type of diary entry is tried instead of just not producing 
any events.

(2) Improper parsing of diary sexps (using regexes instead of e.g. 
`read') leads to diary sexps not being able to span multiple lines or 
have more than a single closing parenthesis (i.e. any sort of nested 
expression).

(3) Not strictly in the scope of icalendar itself, but still related the 
handling of diary sexps: Org's parser seems to assume that each diary 
sexp is on a single line. This and the two limitations above end up 
propagating to ox-icalendar.

hokomo