Fix chunk_unmap() to propagate dirty state.

Fix chunk_unmap() to propagate whether a chunk is dirty, and modify
dirty chunk purging to record this information so it can be passed to
chunk_unmap().  Since the broken version of chunk_unmap() claimed that
all chunks were clean, this resulted in potential memory corruption for
purging implementations that do not zero (e.g. MADV_FREE).

This regression was introduced by
ee41ad409a (Integrate whole chunks into
unused dirty page purging machinery.).

include/jemalloc/internal/chunk.h

@@ -47,7 +47,7 @@ void	*chunk_alloc_default(void *new_addr, size_t size, size_t alignment,
 void	chunk_record(arena_t *arena, extent_tree_t *chunks_szad,
     extent_tree_t *chunks_ad, bool dirty, void *chunk, size_t size);
 bool	chunk_dalloc_default(void *chunk, size_t size, unsigned arena_ind);
-void	chunk_unmap(arena_t *arena, void *chunk, size_t size);
+void	chunk_unmap(arena_t *arena, bool dirty, void *chunk, size_t size);
 bool	chunk_boot(void);
 void	chunk_prefork(void);
 void	chunk_postfork_parent(void);