Change how data is stored in the library. To simplify things, the index

Change how data is stored in the library. To simplify things, the index
(=directory) entry is now shorter, and additional data necessary for checking
in the archiver is not stored in the directory but read from the object file
data in the library.

git-svn-id: svn://svn.cc65.org/cc65/trunk@4944 b7a2c559-68d2-44c3-8de9-860c34a00d81