sort: Avoid linear realloc loops

These interact quite poorly with MRS with revocation enabled, which implements
realloc() by always creating a new allocation.  Even a modification to return
the original pointer if its bounds satisfy the request doesn't help much there.

Apply a simple bandaid: grow the allocation exponentially.  This has no major
downside except when virtual address space is scarce, and that's something we
don't typically worry about.  There doesn't appear to be any explicit
justification for growing buffers so conservatively.

usr.bin/sort/file.c

@@ -297,7 +297,7 @@ sort_list_add(struct sort_list *l, struct bwstring *str)
 		size_t indx = l->count;
 
 		if ((l->list == NULL) || (indx >= l->size)) {
-			size_t newsize = (l->size + 1) + 1024;
+			size_t newsize = (l->size + 1) * 2;
 
 			l->list = sort_realloc(l->list,
 			    sizeof(struct sort_list_item*) * newsize);

usr.bin/sort/radixsort.c

@@ -232,7 +232,7 @@ add_to_sublevel(struct sort_level *sl, struct sort_list_item *item, size_t indx)
 	}
 
 	if (++(ssl->tosort_num) > ssl->tosort_sz) {
-		ssl->tosort_sz = ssl->tosort_num + 128;
+		ssl->tosort_sz = ssl->tosort_num * 2;
 		ssl->tosort = sort_realloc(ssl->tosort,
 		    sizeof(struct sort_list_item*) * (ssl->tosort_sz));
 	}
@@ -245,7 +245,7 @@ add_leaf(struct sort_level *sl, struct sort_list_item *item)
 {
 
 	if (++(sl->leaves_num) > sl->leaves_sz) {
-		sl->leaves_sz = sl->leaves_num + 128;
+		sl->leaves_sz = sl->leaves_num * 2;
 		sl->leaves = sort_realloc(sl->leaves,
 		    (sizeof(struct sort_list_item*) * (sl->leaves_sz)));
 	}