Squashed commits. stringers.go, enumconv

commit 29985f907cfaae7ad605851cf62c6c2fed0b2153
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Wed Jan 23 22:44:37 2013 +1100

    move enumconv under gsnmp

commit c32500e036f8f1661c1c4c8d6d39f899ce3dd749
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Wed Jan 23 15:38:39 2013 +1100

    comments about go_cog

commit 4249c0bc014f8cbe820c99d8fffc4ab1e0cae53c
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Wed Jan 23 15:13:28 2013 +1100

    GNetSnmpSecLevel using gocog and enumconv

commit af4f68dc4fbdefbafc37e15ae2e474b0c03912bd
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Wed Jan 23 10:36:56 2013 +1100

    split into stringers.go