Fixed incorrect order of storing manifest entries

Initial code did not actually sort the manifest sections which are outputted. Check with:

    $ touch a b
    $ jar cf test.jar b a   # Note the order of arguments, b goes first
    $ manifest -c test.jar
    Manifest-Version: 1.0
    
    Name: b
    MD5-Digest: dcje2pRsfN6UtLyl4AFmFw==
    SHA1-Digest: tmZ2kcNfEY7tfoFOZaOJMjI/cBU=
    
    Name: a
    MD5-Digest: 1B2M2Y8AsgTpgAmY7PhCfg==
    SHA1-Digest: 2jmj7l5rSw0yVb/vlWAYkK/YBwk=

Entries in the result are not sorted. This patch fixes it.