Shrink table of contents header

We aren't gonna need 2^32 uids/gids, this is a package manager, not a
file system. Also, mode only uses 16 of 32 bits. We can shrink the
entire header to 8 bytes.

Signed-off-by: David Oberhollenzer <goliath@infraroot.at>

doc/fileformat.md

@@ -105,14 +105,10 @@ table of contents contains an entry with the following common structure:
 
           0       1       2       3
       +-------+-------+-------+-------+
-    0 |              mode             |
+    0 |     mode      |    user id    |
       +-------+-------+-------+-------+
-    1 |            user id            |
+    1 |   group id    |  path length  |
       +-------+-------+-------+-------+
-    2 |           group id            |
-      +-------+-------+-------+-------+
-    3 |  path length  |
-      +---------------+
 
 The mode field contains standard UNIX permissions. The user ID and group ID
 fields contain the numeric IDs of the user and group respectively that own
@@ -142,8 +138,6 @@ On the bit level, the mode field is structured as follows:
         |   +------------------------- set UID bit
         +----------------------------- file type
 
-The upper 16 bit of the mode filed must be set to zero.
-
 Currently, the following file types are supported:
 
 * `S_IFCHR` with a value of 2. The entry defines a character device.

include/pkg/pkgformat.h

@@ -36,10 +36,9 @@ typedef struct {
 } record_t;
 
 typedef struct {
-	uint32_t mode;
-	uint32_t uid;
-	uint32_t gid;
-
+	uint16_t mode;
+	uint16_t uid;
+	uint16_t gid;
 	uint16_t path_length;
 	/* uint8_t path[]; */
 } toc_entry_t;