blame: provide type of fingerprints pointer

The fingerprints member of struct blame_origin is a void pointer that is
only ever used to reference objects of type struct fingerprint.  Declare
its type to allow the compiler to do type checks.  We can keep its type
opaque in blame.h, though -- only functions in blame.c need to know the
actual definition of struct fingerprint.

Signed-off-by: René Scharfe <l.s.r@web.de>
Reviewed-by: Barret Rhoden <brho@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

blame.h

@@ -16,6 +16,8 @@
 #define BLAME_DEFAULT_MOVE_SCORE	20
 #define BLAME_DEFAULT_COPY_SCORE	40
 
+struct fingerprint;
+
 /*
  * One blob in a commit that is being suspected
  */
@@ -52,7 +54,7 @@ struct blame_origin {
 	struct blame_entry *suspects;
 	mmfile_t file;
 	int num_lines;
-	void *fingerprints;
+	struct fingerprint *fingerprints;
 	struct object_id blob_oid;
 	unsigned short mode;
 	/* guilty gets set when shipping any suspects to the final