bus: unmap memfd retrieved from the memfd cache
man: mention that units are 1024-based
keymap: add some more Asus laptop keys

With Linux 3.9 (commit a935eaecef2b209ad661dadabb4e32b7c9a9b924), the
Asus keyboard driver has changed to be more compliant to the symbol
signification. This has led to some issues with udev. In particular,
the XF86TouchpadToggle (a Fn key) does not work anymore on Asus X52J.

I found another similar patch which does not seem to have been ever
submitted/merged:

  https://launchpadlibrarian.net/73337842/95-keymap.rules.patch

Find enclosed the patch containing both the launchpad patch and mine
into one file.

https://bugs.freedesktop.org/show_bug.cgi?id=65375