merge-ort: add a few includes

Include blob.h for definition of blob_type, and commit-reach.h for
declarations of get_merge_bases() and in_merge_bases().  While none of
these are used yet, we want to avoid cross-dependencies in the next
three series of patches for merge-ort and merge them at the end; adding
these "#include"s now avoids textual conflicts.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

merge-ort.c

@@ -17,7 +17,9 @@
 #include "cache.h"
 #include "merge-ort.h"
 
+#include "blob.h"
 #include "cache-tree.h"
+#include "commit-reach.h"
 #include "diff.h"
 #include "diffcore.h"
 #include "dir.h"