elf.py: remove StaticLibFile; ArFile.compare_details() is much better

Remove the old code in the StaticLibFile class as it now duplicates the
recursion in ArFile.compare_details() in a much inferior way. Fixes
issue #64, see the multiple use cases there and in the next commit
adding tests.

The patch header line in the test output is decremented one line because
when run on .a files readelf inserted headings like this:

  In archive test1.a:

Signed-off-by: Marc Herbert <Marc.Herbert@gmail.com>