Remove some obsolete integer overflow handling

* lisp/subr.el (number-sequence):
* lisp/org/org-gnus.el (org-gnus-follow-link):
* lisp/ls-lisp.el (ls-lisp-insert-directory):
Remove dead code guarding against integer overflow.

lisp/ls-lisp.el

@@ -420,14 +420,7 @@ not contain `d', so that a full listing is expected."
 		  attr (cdr elt)
 		  file-size (file-attribute-size attr))
 	    (and attr
-		 (setq sum (+ file-size
-			      ;; Even if neither SUM nor file's size
-			      ;; overflow, their sum could.
-			      (if (or (< sum (- 134217727 file-size))
-				      (floatp sum)
-				      (floatp file-size))
-				  sum
-				(float sum))))
+		 (setq sum (+ file-size sum))
 		 (insert (ls-lisp-format short attr file-size
 					 switches time-index))))
 	  ;; Insert total size of all files:

lisp/org/org-gnus.el

@@ -242,9 +242,7 @@ If `org-store-link' was called with a prefix arg the meaning of
 	      (_
 	       (let ((articles 1)
 		     group-opened)
-		 (while (and (not group-opened)
-			     ;; Stop on integer overflows.
-			     (> articles 0))
+		 (while (not group-opened)
 		   (setq group-opened (gnus-group-read-group articles t group))
 		   (setq articles (if (< articles 16)
 				      (1+ articles)

lisp/subr.el

@@ -681,14 +681,12 @@ of course, also replace TO with a slightly larger value
     (when (zerop inc) (error "The increment can not be zero"))
     (let (seq (n 0) (next from) (last from))
       (if (> inc 0)
-          ;; The (>= next last) condition protects against integer
-          ;; overflow in computing NEXT.
-          (while (and (>= next last) (<= next to))
+          (while (<= next to)
             (setq seq (cons next seq)
                   n (1+ n)
                   last next
                   next (+ from (* n inc))))
-        (while (and (<= next last) (>= next to))
+        (while (>= next to)
           (setq seq (cons next seq)
                 n (1+ n)
                 next (+ from (* n inc)))))