bug#33695: 27.0.50; which-function reports wrong imenu information

[martin rudalics <rudalics@gmx.at>]

 > Thanks for the reply. This seems to work well, though I haven't tried it
 > in an enormous buffer.

Maybe we should make it optional so people on slower machines have the
choice.  I have no opinion because I don't use 'which-func-mode' hence
people who do should chime in.

For me the idea of calculating all function position in a buffer and
afterwards have 'which-func-mode' scan them to find out which function
point is in, strikes me as enormous over-kill.  In particular with
'syntax-ppss' around which usually should, without any additional
cost, provide the position where the current functions starts via the
9th element of its return value.  But don't let these rantings
distract you.

martin