Make single bit bitfields unsigned to avoid clang 16 warning (libarch…

…ive#1860)

Clang 16 introduced a warning about single bit bitfields in structs,
which is triggered by a few libarchive formats:

libarchive/archive_write_set_format_7zip.c:1541:13: error: implicit
truncation from 'int' to a one-bit wide bit-field changes value from 1
to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
                    file->dir = 1;
                              ^ ~

This is because single bit bitfields only support values -1 and 0, if
they are signed.

For bitfields with two or more bits this can be intentional, but single
bit bitfields are typically used as booleans, so it is better to make
them unsigned.

(cherry picked from commit f180dca)

libarchive/archive_write_set_format_7zip.c

@@ -165,7 +165,7 @@ struct file {
 	mode_t			 mode;
 	uint32_t		 crc32;
 
-	signed int		 dir:1;
+	unsigned		 dir:1;
 };
 
 struct _7zip {

libarchive/archive_write_set_format_iso9660.c

@@ -289,12 +289,12 @@ struct isoent {
 		struct extr_rec	*current;
 	}			 extr_rec_list;
 
-	signed int		 virtual:1;
+	unsigned int		 virtual:1;
 	/* If set to one, this file type is a directory.
 	 * A convenience flag to be used as
 	 * "archive_entry_filetype(isoent->file->entry) == AE_IFDIR".
 	 */
-	signed int		 dir:1;
+	unsigned int		 dir:1;
 };
 
 struct hardlink {
@@ -755,9 +755,9 @@ struct iso9660 {
 
 	/* Used for making zisofs. */
 	struct {
-		signed int	 detect_magic:1;
-		signed int	 making:1;
-		signed int	 allzero:1;
+		unsigned int	 detect_magic:1;
+		unsigned int	 making:1;
+		unsigned int	 allzero:1;
 		unsigned char	 magic_buffer[64];
 		int		 magic_cnt;
 
@@ -7802,8 +7802,8 @@ struct zisofs_extract {
 	uint64_t	 pz_uncompressed_size;
 	size_t		 uncompressed_buffer_size;
 
-	signed int	 initialized:1;
-	signed int	 header_passed:1;
+	unsigned int	 initialized:1;
+	unsigned int	 header_passed:1;
 
 	uint32_t	 pz_offset;
 	unsigned char	*block_pointers;

libarchive/archive_write_set_format_xar.c

@@ -212,8 +212,8 @@ struct file {
 	struct heap_data	 data;
         struct archive_string    script;
 
-	signed int		 virtual:1;
-	signed int		 dir:1;
+	unsigned int		 virtual:1;
+	unsigned int		 dir:1;
 };
 
 struct hardlink {