libsparse: deal with build warning messages

- mostly unused parameters, added defs.h to hold __unused macro
- read_all prototype not included, added output_file.h to acquire

Change-Id: Ib7ee00614acab53a6bd6a64f7e26a8c13dbe6297
diff --git a/libsparse/output_file.c b/libsparse/output_file.c
index e63c4a9..1cf8d8d 100644
--- a/libsparse/output_file.c
+++ b/libsparse/output_file.c
@@ -29,6 +29,7 @@
 #include <unistd.h>
 #include <zlib.h>
 
+#include "defs.h"
 #include "output_file.h"
 #include "sparse_format.h"
 #include "sparse_crc32.h"
@@ -264,7 +265,7 @@
 	.close = gz_file_close,
 };
 
-static int callback_file_open(struct output_file *out, int fd)
+static int callback_file_open(struct output_file *out __unused, int fd __unused)
 {
 	return 0;
 }
@@ -287,7 +288,7 @@
 	return 0;
 }
 
-static int callback_file_pad(struct output_file *out, int64_t len)
+static int callback_file_pad(struct output_file *out __unused, int64_t len __unused)
 {
 	return -1;
 }
@@ -631,8 +632,8 @@
 }
 
 struct output_file *output_file_open_callback(int (*write)(void *, const void *, int),
-		void *priv, unsigned int block_size, int64_t len, int gz, int sparse,
-		int chunks, int crc)
+		void *priv, unsigned int block_size, int64_t len,
+		int gz __unused, int sparse, int chunks, int crc)
 {
 	int ret;
 	struct output_file_callback *outc;