Extension for IPv4Reassembler to prevent a possible memory leak

[erikbasargin]

Hello!
I noticed that there is no removal of obsolete packages. If there is a loss in traffic, there will be a memory leak in IPv4Reassembler (IPv4Stream::fragments_type).
Added two options to prevent this.
On the similarity pcapplusplus added the ability to limit the streams (set_max_number_packets_to_stream).
And also added the removal of expired streams by the calculation of the time of their lives (set_timeout_to_stream).

In a hurry, added support for C++ below 11 version. :) But we need to check in more detail - could be broken cross-platform.

Tested in Linux: Arch [gcc 8.1.1 or clang++ 6.0.0] and CentOS7 [gcc 4.8.3].
Problems occurred in the tests for СentOS7, when we set the flag -DLIBTINS_ENABLE_CXX11=0.
The error is related to enum in class IPv6 (While it did not fix it, but maybe it could be similar):
/home/dev/work/projects/libtins-origin/tests/src/ipv6_test.cpp: В функции-члене «virtual void IPv6Test_HopByHopPadding_Test::TestBody()»: /home/dev/work/projects/libtins-origin/tests/src/ipv6_test.cpp:366:34: ошибка: «Tins::IPv6::ExtensionHeader» is not a class or namespace ipv6_header.add_header(IPv6::ExtensionHeader::HOP_BY_HOP); ^ /home/dev/work/projects/libtins-origin/tests/src/ipv6_test.cpp: В функции-члене «virtual void IPv6Test_HopByHopParsing_Test::TestBody()»: /home/dev/work/projects/libtins-origin/tests/src/ipv6_test.cpp:377:67: ошибка: «Tins::IPv6::ExtensionHeader» is not a class or namespace const IPv6::ext_header* ext_header = ipv6.search_header(IPv6::ExtensionHeader::HOP_BY_HOP);

Is there a need for C++ support below version 11? I would say that this is an old version :).