bug#41006: 26.3; regular expressions documentation

[Mattias Engdegård]

The disposition of the regexp documentation could be improved, yes. Currently 
it's arranged by syntax, which is the implementor's view, rather than by 
function, which is the user's. Condensing related text into a single page would 
help. (Cf. the more recently written section on rx in Emacs 27.)

The manual does say

‘\{M,N\}’
     [...] If M is omitted, the minimum is 0; if N is omitted, there is no 
maximum.

so you may be mistaken on that point.

The \= anchor is probably less frequently used than the other zero-width 
assertions such as $, \< etc but does come in handy occasionally. It's there in 
case you need it.