env: re-add support for auto-completion

Currently, only basic completion is supported (no globs), but this is
what we had previously.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

include/common.h

@@ -632,6 +632,7 @@ static inline IPaddr_t getenv_IPaddr (char *var)
 /* lib/qsort.c */
 void qsort(void *base, size_t nmemb, size_t size,
 	   int(*compar)(const void *, const void *));
+int strcmp_compar(const void *, const void *);
 
 /* lib/time.c */
 void	udelay        (unsigned long);

include/search.h

@@ -74,6 +74,13 @@ extern void hdestroy_r(struct hsearch_data *__htab);
 extern int hsearch_r(ENTRY __item, ACTION __action, ENTRY ** __retval,
 		     struct hsearch_data *__htab);
 
+/*
+ * Search for an entry matching `MATCH'.  Otherwise, Same semantics
+ * as hsearch_r().
+ */
+extern int hmatch_r(const char *__match, int __last_idx, ENTRY ** __retval,
+		    struct hsearch_data *__htab);
+
 /* Search and delete entry matching ITEM.key in internal hash table. */
 extern int hdelete_r(const char *__key, struct hsearch_data *__htab);