By using the build system's library-selection mechanism instead of many
timer targets with different 'REQUIRES' declarations, this patch reduces
the noise of the build system. For all platforms, the target at
'os/src/drivers/timer' is built. The target, in turn, depends on a
'timer' library, which is platform-specific. The various library
description files are located under 'os/lib/mk/<platform>'. The common
bits are contained in 'os/lib/mk/timer.inc'.
The generic parent_cap.cc overwrote the beginning of the data segment with
to much. Reserved are solely 16 byte, for 64bit we use however 32byte.
Actually, the parent_cap copying is not required at all. The parent cap
selector is at a fixed define place, so that no exported symbols are required
for determination of the parent_cap.
Remove it.
