lwip: purge PCBs in time-wait state more quickly

Fixes #33.
NOVA: make noux_tool_chain happy

Multiple calls to get the dataspace capability on NOVA lead to the situation
that the caller gets each time a new mapping of the same capability at
different indexes.

The client/caller assumes to get every time the very same index, e.g. in
Noux the index is used to look up structures.

Cache the dataspace capability returned via a rm_session for base-nova.
libports: add pcre-8.3 (8bit only)

For it is enough to just provide the 8bit version of pcre.
libports: add poll() to libc

Implements poll() via select() for certain programs like OpenSSH
which need it.

(This implementation is actually based OpenSSHp's compat function.)
Noux: add noux-pkg/lighttpd
Let git ignore libports/include/ncurses/ncurses.h
libc: Add munmap support to plugin interface

With this patch, libc plugins become able to handle munmap for regions
attached by the plugin.
tar_rom: Ignore leading './' in tar archives
Add mmap and nunmap to libc_noux, libc_fs

In the current form, only PROT_READ is supported. This case is emulated
by copying the file content into new allocated backing store. Even
though the performance benefits of mmap-using code will not be
preserved, code that relies on mmap can be executed via the libc_noux
or libc_fs plugins, i.e. lightttpd.
Native version of lighttpd

The port of lighttpd at 'ports/src/app/lighttpd' executes the web server
directly (w/o using Noux). It is accompanied by the lighttpd.run script.

At the current stage, lighttpd is starting up but fails because of an
unsupport fcntl call.
Noux: add noux_net_lighttpd.run

This patch adds lighttpd as noux package. However, we do not use the
original build system but rather compile lighttpd directly from the
Genode build system. This is needed because we want to statically link
lighttpd modules into the binary. This mode is (somehow) supported by
the SConscript that comes with lighttpd. However, the GNU build scripts
do not expose this feature.
Noux: change default --prefix in noux.mk

The directory specified by --prefix is not only used to determine
the install location but is also used by -rpath. Therefor it is
better to use $(DESTDIR) to install the binaries to the right
directory and to use --prefix to express the actual location within
NOUX.
libports: enable SO_REUSEADDR in lwip
ACPI: Allow PCI slave to use CPU sessions
ACPI: Fix offsets when mapping I/O mem

Fixes #309
noux: pass correct mode to Fs_vfs_handle

This patch resolves a problem with running 'noux_gdb.run'. Right at the
start, GDB would output a message like:

  ...cli-script.c:1614: internal-error: called with NULL file pointer!
  A problem internal to GDB has been detected,
  further debugging may prove unreliable.
  Quit this debugging session? (y or n)

The LOG output hints at the cause of the problem:

  [init -> noux -> /bin/genode-x86-gdb] fcntl: F_GETFL for libc_fd=3

Thanks to cproc for the fix!
Noux: Toggle syscall tracing via config

Noux used to trace syscalls by default, which significantly slows down
its execution. This patch disables the tracing by default. It can be
enabled by specifying 'trace_syscalls="yes"' attribute to the Noux
configuration.
Compile warning fix
lwip: Convert fcntl argument, add missing defs
libc: Unregister region on nunmap