Cygwin: Update search.h functions for POSIX.1-2024

Add type posix_tnode.  Change certain uses of "void" to "posix_tnode" in
both the prototypes and definitions of functions associated with <search.h>.

(Necessary changes to Newlib's /libc/include/search.h have already been
submitted in a patch sent to [email protected].)

Reported-by: Collin Funk <[email protected]>
Addresses: https://cygwin.com/pipermail/cygwin/2025-April/258032.html
Signed-off-by: Mark Geisert <[email protected]>
Fixes: ec98d19 "* wininfo.h (wininfo::timer_active): Delete."
(cherry picked from commit e6b915d)

Author: mgeisert

winsup/cygwin/include/search.h

@@ -39,6 +39,8 @@ typedef	struct node
 } node_t;
 #endif
 
+typedef void posix_tnode;
+
 struct hsearch_data
 {
   struct internal_head *htable;
@@ -58,13 +60,13 @@ ENTRY *hsearch (ENTRY, ACTION);
 int hcreate_r (size_t, struct hsearch_data *);
 void hdestroy_r (struct hsearch_data *);
 int hsearch_r (ENTRY, ACTION, ENTRY **, struct hsearch_data *);
-void *tdelete (const void * __restrict, void ** __restrict,
+void *tdelete (const void * __restrict, posix_tnode ** __restrict,
 	       int (*) (const void *, const void *));
 void tdestroy (void *, void (*)(void *));
-void *tfind (const void *, void **,
+posix_tnode *tfind (const void *, posix_tnode *const *,
 	     int (*) (const void *, const void *));
-void *tsearch (const void *, void **, int (*) (const void *, const void *));
-void  twalk (const void *, void (*) (const void *, VISIT, int));
+posix_tnode *tsearch (const void *, posix_tnode **, int (*) (const void *, const void *));
+void  twalk (const posix_tnode *, void (*) (const posix_tnode *, VISIT, int));
 void *lfind (const void *, const void *, size_t *, size_t,
 	     int (*) (const void *, const void *));
 void *lsearch (const void *, void *, size_t *, size_t,