gems: new backdrop application

The new backdrop found at gems/src/app/backdrop replaces the old program
that was hosted in the demo repository.
terminal_log: don't write null-termination to terminal

Fixes #1231.
Qt5: migrate to new ports mechanism

Fixes #1233.
GCC: migrate to new ports mechanism

Fixes #1234.
GBD: migrate to new ports mechanism

Fixes #1237.
wm: fix WHEEL event translation

Fixes #1242.
vfs: add vfs handle header to single_file header

Fixes #1238.
vfs: add Rtc_file_system

The Rtc_file_system reads the current time from a Rtc_session and
provides the time as '%Y-%m-%d %H:%M\n' to all users of the vfs
node.

Fixes #1238.
openssl: use Genode specific RAND backend

The backend merely provides simpler access to '/dev/random' because
on Genode the common random device checks are unnecessary.

Fixes #1236.
openssl: update to version 1.0.1i

Just a normal version bump, though we should revise the openssl port
regarding explicit memset() etc. issues.

Fixes #1236.
libssl: use platform specific mk files

Instead of checking the target platform in the mk file use the common
pattern of providing a mk file for each platform.

Fixes #1236.
libcrypto: use platform specific mk files

Instead of checking the target platform in the mk file use the common
pattern of providing a mk file for each platform.

Fixes #1236.
libcrypto: remove MD2, RC5 and store

Remove components that are disabled upstream.

Fixes #1236.
libc: add support for Rtc_file_system

Fixes #1241.
libc: utilize Rtc_file_system in time functions

Fixes #1241.
libc: add support for external vfs file systems

These file systems are provided on-demand by loading a shared library
when the fstab node is traversed. By convention this library is named
after the file system it provides. For example a file system that
provides a 'random' file system node is called 'vfs_random.lib.so'. It
is still possible to give the the node another name in the vfs. The
following code snippts illustrates this matter:

! [...]
! <config>
!   <libc>
!     <vfs>
!       <dir name="dev"> <jitterentropy name="random"/> </dir>
!     </vfs>
!   </libc>
! </config>
! [...]

Here the jitterentropy file system, implemented in
'vfs_jitterentropy.lib.so' provides a file system node named 'random'
in the 'dev' directory. When traversing the vfs section the libc will
try to load 'vfs_jitterentropy.lib.so' but programs may access the
file system only via '/dev/random'.

Fixes #1240.
libports: add vfs_jitterentropy library

This commit adds a port the jitterentropy library to Genode. As backend
on x86_{32,64} 'rdtsc' is used and on ARMv{6,7} the performance-counter.

Fixes #1239.
libc: add if_tun.h

Fixes #1235.
ports: add openvpn-2.3.4

The port was succesfully tested a echo test and lighttpd. DHCP over
OpenVPN is not tested and probably will not work out of the box.
Therefore, the ip address etc. need to be specified manually.

For now, only ethernet bridging (using a TAP device) is supported.

Fixes #1235.
libc: add net/route.h and its dependencies

Fixes #1235.