Add quarantine unit tests.

Verify that freed regions are quarantined, and that redzone corruption
is detected.

Introduce a testing idiom for intercepting/replacing internal functions.
In this case the replaced function is ordinarily a static function, but
the idiom should work similarly for library-private functions.

include/jemalloc/internal/arena.h

@@ -405,7 +405,13 @@ void	arena_tcache_fill_small(arena_t *arena, tcache_bin_t *tbin,
     size_t binind, uint64_t prof_accumbytes);
 void	arena_alloc_junk_small(void *ptr, arena_bin_info_t *bin_info,
     bool zero);
+#ifdef JEMALLOC_JET
+typedef void (arena_redzone_corruption_t)(void *, size_t, bool, size_t,
+    uint8_t);
+extern arena_redzone_corruption_t *arena_redzone_corruption_fptr;
+#endif
 void	arena_dalloc_junk_small(void *ptr, arena_bin_info_t *bin_info);
+void	arena_quarantine_junk_small(void *ptr, size_t usize);
 void	*arena_malloc_small(arena_t *arena, size_t size, bool zero);
 void	*arena_malloc_large(arena_t *arena, size_t size, bool zero);
 void	*arena_palloc(arena_t *arena, size_t size, size_t alignment, bool zero);

include/jemalloc/internal/private_symbols.txt

@@ -50,8 +50,10 @@ arena_prof_ctx_set
 arena_prof_promoted
 arena_ptr_small_binind_get
 arena_purge_all
+arena_quarantine_junk_small
 arena_ralloc
 arena_ralloc_no_move
+arena_redzone_corruption
 arena_run_regind
 arena_salloc
 arena_stats_merge