libc: export LIBC_REP_DIR in libc-common.inc

This information is useful if 'libc-common.inc' is included from
another repository, i.e., for building stripped-down libc variants
tailored to an individual application.
libc: Add sys/disk.h

Needed by the POSIX backend of the VirtualBox runtime.
libc: Dummy for sys/user.h
base: Add Allocator_avl::size_at function

This function provides a way to request the size of an previously
allocated block. It is useful to to ease the implementation of realloc
functionality based on Allocator_avl.
libc: Add Libc::Mem_alloc::size_at

Adding this function eases the implementation of realloc based on
'Libc::Mem_alloc'. Note that this allocator is not used by libc's
default malloc implementation but it is useful for customized C
runtimes, e.g., for the runtime of VirtualBox.
framebuffer: fix ambiguity for strncpy
pthread: limit timeouts to >= 10 ms

The timed semaphore supports a minimum timeout of 10 ms and logs a
warning if the timeout is lower than the minimum. To prevent the
warning, we limit timeouts to >= 10 ms.
pthread: catch time out exception
base: add flex page iterator

Issue #8
nova: support noreturn attribute for syscall reply
nova: update syscall bindings
nova: use kernel branch with vCPU fpu support

branch r4 based on latest vanilla kernel of @udosteinberg
nova: add feature to yield a thread

used by virtualbox intensively
nova: fix utcb layout for 32bit

Makes virtualbox as 32bit VMM working
nova: for clearing a ds it must be ever writable
nova: nopcid required for thinkpad x201
lx_fs: Support large files on 32-bit machines
libc_fs: Handle Packet_alloc_failed exception
libc_fs fix of leaking allocation in stream
ports: add VirtualBox as VMM for Genode

Fixes #1055