decompress_bunzip2: handle concatenated .bz2 files

function                                             old     new   delta
unpack_bz2_stream                                    207     307    +100
start_bunzip                                         199     209     +10
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 110/0)             Total: 110 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/unarchive.h b/include/unarchive.h
index b55af6d..11d8c77 100644
--- a/include/unarchive.h
+++ b/include/unarchive.h
@@ -193,7 +193,7 @@
 
 /* A bit of bunzip2 internals are exposed for compressed help support: */
 typedef struct bunzip_data bunzip_data;
-int start_bunzip(bunzip_data **bdp, int in_fd, const unsigned char *inbuf, int len) FAST_FUNC;
+int start_bunzip(bunzip_data **bdp, int in_fd, const void *inbuf, int len) FAST_FUNC;
 int read_bunzip(bunzip_data *bd, char *outbuf, int len) FAST_FUNC;
 void dealloc_bunzip(bunzip_data *bd) FAST_FUNC;