Make 'load-dangerous-libraries' obsolete (Bug#37819)

When 'load-dangerous-libraries' was t, Emacs allowed loading .elc
files compiled by XEmacs.  This patch removes the support for that use
case, and declares the variable obsolete.

* lisp/subr.el (load-dangerous-libraries): Declare obsolete.
* src/lread.c (Fload): Ignore its value, and thereby refuse to load
files byte compiled by XEmacs.
(syms_of_lread): Update doc string of 'bytecomp-version-regexp' to not
refer to it.
* doc/emacs/building.texi (Lisp Libraries): Remove its documentation.

1 files changed, 3 insertions, 0 deletions

diff --git a/lisp/subr.el b/lisp/subr.el
index b5ec0de156a..96b98c6a5b3 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -1621,6 +1621,9 @@ be a list of the form returned by `event-start' and `event-end'."
 (defvaralias 'messages-buffer-max-lines 'message-log-max)
 (define-obsolete-variable-alias 'inhibit-null-byte-detection
   'inhibit-nul-byte-detection "27.1")
+(make-obsolete-variable 'load-dangerous-libraries
+                        "no longer used." "27.1")
+
 
 ;;;; Alternate names for functions - these are not being phased out.