Added start of libarchive bindings for writing

src/archive.v

@@ -0,0 +1,85 @@
+// Bindings for the libarchive library
+
+#flag -larchive
+
+#include "archive.h"
+
+struct C.archive {}
+
+// Create a new archive struct for reading
+fn C.archive_read_new() &C.archive
+
+// Configure the archive to work with zstd compression
+fn C.archive_read_support_filter_zstd(&C.archive)
+
+// Configure the archive to work with a tarball content
+fn C.archive_read_support_format_tar(&C.archive)
+
+// Open an archive for reading
+fn C.archive_read_open_filename(&C.archive, &char, int) int
+
+// Go to next entry header in archive
+fn C.archive_read_next_header(&C.archive, &&C.archive_entry) int
+
+// Skip reading the current entry
+fn C.archive_read_data_skip(&C.archive)
+
+// Free an archive
+fn C.archive_read_free(&C.archive) int
+
+// Read an archive entry's contents into a pointer
+fn C.archive_read_data(&C.archive, voidptr, int)
+
+// Create a new archive struct for writing
+fn C.archive_write_new() &C.archive
+
+// Sets the filter for the archive to gzip
+fn C.archive_write_add_filter_gzip(&C.archive)
+
+// Sets to archive to "pax restricted" mode. Libarchive's "pax restricted"
+// format is a tar format that uses pax extensions only when absolutely
+// necessary. Most of the time, it will write plain ustar entries. This is the
+// recommended tar format for most uses. You should explicitly use ustar format
+// only when you have to create archives that will be readable on older
+// systems; you should explicitly request pax format only when you need to
+// preserve as many attributes as possible.
+fn C.archive_write_set_format_pax_restricted(&C.archive)
+
+// Opens up the filename for writing
+fn C.archive_write_open_filename(&C.archive, &char)
+
+// Write an entry to the archive file
+fn C.archive_write_header(&C.archive, &C.archive_entry)
+
+#include "archive_entry.h"
+
+struct C.archive_entry {}
+
+// Create a new archive_entry struct
+fn C.archive_entry_new() &C.archive_entry
+
+// Get the filename of the given entry
+fn C.archive_entry_pathname(&C.archive_entry) &char
+
+// Get an entry's file size
+// Note: this function actually returns an i64, but as this can't be used as an
+// arugment to malloc, we'll just roll with it & assume an entry is never
+// bigger than 4 gigs
+fn C.archive_entry_size(&C.archive_entry) int
+
+// Set the pathname for the entry
+fn C.archive_entry_set_pathname(&C.archive_entry, &char)
+
+// Sets the file size of the entry
+fn C.archive_entry_set_size(&C.archive_entry, i64)
+
+// Sets the file type for an entry
+fn C.archive_entry_set_filetype(&C.archive_entry, u32)
+
+// Sets the file permissions for an entry
+fn C.archive_entry_set_perm(&C.archive_entry, int)
+
+#include <string.h>
+
+// Compare two C strings; 0 means they're equal
+fn C.strcmp(&char, &char) int