L4Linux: fix usage of l4_touch_xx (fix #682)

Use size in bytes, when touching memory via l4_touch_ro or l4_touch_rw, instead
of log2 size.
base-foc: remove links to obsolete initrd archives

Fix #686
Remove 'epit' from generic i.MX platform spec

Remove the 'epit' variable from the generic imx31 and imx53 specification,
and only add it to base-hw specific i.MX specs. Thereby the EPIT timer
library gets build for base-hw only.
Moreover, fix some const-ness issues in the platform_timer implementation
for the EPIT timer.
Fixes #688.
foc: Select "thread-ready" bit in pause function
foc: Extend irq mode heuristics

Explicitly set default mode for legacy interrupts to not rely on kernel
default settings. This patch fixes the constantly busy IRQ threads for
IRQ 1 and 12 as soon as the PS/2 driver was loaded until the point when
the first IRQ occurred.
Use ccache for Fiasco.OC, ignore L4re build errors

This patch is a temporary hack to accelerate the work on Fiasco.OC while
removing sigma0.
foc: Remove dead code
bomb.run: Increase timer quota

With the original quota, the test does not run on foc_x86_32.
foc: Don't touch pages in page-fault handling
foc: Coding style
core: Clear allocated memory

Note that this patch changes the signature of
'Core_mem_alloc::_map_local'. The third argument used to be a log2 size.
The new version uses a plain size argument to be more consistent with
the rest of core.
foc: Remove sigma0 (WiP)