CPP: Add "system" as a Boost component.

This is required with newer Boost (starting with 1.50).

R=daniel@pocock.pro
BUG=

Review URL: https://codereview.appspot.com/100910043

git-svn-id: http://libphonenumber.googlecode.com/svn/trunk@667 ee073f10-1060-11df-b6a4-87a95322a99c
Modernize debian/ and add multiarch support and hardening flags.

R=daniel@pocock.pro
BUG=

Review URL: https://codereview.appspot.com/103800043

git-svn-id: http://libphonenumber.googlecode.com/svn/trunk@668 ee073f10-1060-11df-b6a4-87a95322a99c