Fixed a warning wrt modules during the build phase.

Thanks to goranche (https://github.com/goranche) for the hint.
Updated installer to use kernel version 3.12.

The sd_mod kernel module has a new dependency on crct10diff_common, so
included that.
Just in case I also included it's 'sibbling' crct10diff_generic.
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of github.com:goranche/raspbian-ua-netinst