i2pd: new package

i2pd: new package

i2pd (I2P Daemon) is a full-featured C++ implementation of I2P
client.

I2P (Invisible Internet Protocol) is a universal anonymous
network layer.
All communications over I2P are anonymous and end-to-end
encrypted, participants don't reveal their real IP addresses.

http://i2pd.website

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[Thomas:
 - Add third patch to not install the license file in /usr/LICENSE and
   the source code in /usr/src instead of using a post-install-target
   hook to remove /usr/LICENSE and /usr/src. Indeed, we're not sure if
   /usr/src contains only stuff installed by this package.
 - Clarify the comment that explains why -DTHREADS_PTHREAD_ARG=OFF is
   passed, especially because it's only needed for older versions of
   CMake, and causes a warning with newer versions of CMake.
 - Propagate architecture dependencies to the Config.in comment about
   the exception_ptr requirement.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>