docs: add buffer.h & oid.h to types.h

Otherwise docurium/clang chokes on the types, and ignores the documentation comments altogether.

include/git2/stash.h

@@ -9,6 +9,7 @@
 
 #include "common.h"
 #include "types.h"
+#include "checkout.h"
 
 /**
  * @file git2/stash.h

include/git2/transaction.h

@@ -8,6 +8,7 @@
 #define INCLUDE_git_transaction_h__
 
 #include "common.h"
+#include "types.h"
 
 /**
  * @file git2/transaction.h

include/git2/types.h

@@ -63,6 +63,9 @@ typedef int64_t git_time_t;
 
 #endif
 
+#include "buffer.h"
+#include "oid.h"
+
 /** Basic type (loose or packed) of any Git object. */
 typedef enum {
 	GIT_OBJ_ANY = -2,		/**< Object can be any of the following */