Add dependencies for the libphonenumber6-dev package.

The dependencies for this package should be those packages that must be
installed in order to compile and link code that uses the library.

R=daniel@pocock.pro
BUG=

Review URL: https://codereview.appspot.com/137740043

git-svn-id: http://libphonenumber.googlecode.com/svn/trunk@692 ee073f10-1060-11df-b6a4-87a95322a99c