Deleting sysctl.conf entries; multiple entries

[esalberg]

1. Looking through the code, there is an ensure => absent option and there is a destroy function, but I can't seem to get them to work to remove entries in sysctl.conf. Is that functionality supported, or does it need to be written?

2. If there are multiple entries for a sysctl setting, the module appears to update the first one only, which I believe is not the one that is actually read (iirc, later entries take precedence). Should there be an option either to combine duplicate entries and/or update the last entry (or I guess both entries)?

e.g.
kernel.shmmax 10000
kernel.shmmax 12000

I'm willing to work on a pull request if necessary, but I'd like to get input on direction before heading off into code land.