bug#60758: 29.0.60; while-let uses if-let* convention in contradiction to the docstring

[Daniel Mendler]

The docstring of `while-let' says:

     The variable list SPEC is the same as in if-let.

However in the definition `if-let*' is used. `if-let*' differs from
`if-let' since it doesn't support the special single binding form.

     (while-let (var exp)
         ...)

Therefore `if-let*' should be replaced with `if-let' in the definition
of `while-let', bringing the implementation in accordance with the
docstring. The name `while-let' (in contrast to `while-let*') also
suggest that the `if-let' spec is supported.

In GNU Emacs 29.0.60 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.16.0, Xaw scroll bars) of 2022-12-30 built on projects
Repository revision: d086cd6cf877c6ca7af6712f9b79b52dd0caa934
Repository branch: emacs-29
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Debian GNU/Linux 11 (bullseye)