Fix memory leaks in pg_combinebackup/reconstruct.c.

One code path forgot to free the separately-malloc'd filename
part of a struct rfile.  Another place freed the filename but
forgot the struct rfile itself.  These seem worth fixing because
with a large backup we could be dealing with many files.

Coverity found the bug in make_rfile().  I found the other one
by manual inspection.

src/bin/pg_combinebackup/reconstruct.c

@@ -370,6 +370,7 @@ reconstruct_from_incremental_file(char *input_filename,
 		if (s->relative_block_numbers != NULL)
 			pfree(s->relative_block_numbers);
 		pg_free(s->filename);
+		pg_free(s);
 	}
 	pfree(sourcemap);
 	pfree(offsetmap);
@@ -517,6 +518,7 @@ make_rfile(char *filename, bool missing_ok)
 	{
 		if (missing_ok && errno == ENOENT)
 		{
+			pg_free(rf->filename);
 			pg_free(rf);
 			return NULL;
 		}