Finished adding multi-threaded extraction.

Added option in unsquashfs to specify the number of threads used.
Changed some functions to accept an allocator instead of just using
Archive's
Fixed run_tests.sh due to new c libraries

src/file.zig

@@ -56,7 +56,7 @@ pub fn deinit(self: SfsFile) void {
 }
 
 fn getEntries(self: SfsFile) ![]DirEntry {
-    return self.inode.dirEntries(self.archive);
+    return self.inode.dirEntries(self.archive.allocator(), self.archive.*);
 }
 
 pub fn ownerUid(self: SfsFile) !u16 {