Initial migration to kernel 3.9.9 with module signing

Temporarily disabled open-vm-tools due to (#474636).
Upgraded VirtualBox modules and tools.

Migrated iwlwifi firmwares to linux-firmware package.
Extended and reworked devices support, including firmwares.
Removed now-unnecessary custom carl9170-firmware ebuild.

Extended Secure Boot certificates generation with a
derivative kernel modules signing certificate. Non in-tree
modules are signed when necessary after building modules,
in lieu of (#447352).

Extended firmware build-time diagnostics to detect firmware
shipped into INSTALL_FW_PATH during kernel modules install,
if it is not otherwise installed.

Closes (GitHub: #10).
Minor build-time updates

Disabled unnecessary package unmasking.
Added numactl package.
Minor progress with XChat -> HexChat migration.