LICENSE: allow all future versions of LGPLv3+

In case I'm hit by a bus and FSF comes out with an LGPLv4,
the project will still be able to move forward.

While we're at it, update the gemspec, too.

LICENSE

@@ -3,19 +3,17 @@ revision control for names and email addresses of all of them.
 
 You can redistribute it and/or modify it either under the terms of the GNU
 Lesser General Public License as published by the Free Software Foundation,
-version 3.0 {LGPLv3}[http://www.gnu.org/licenses/lgpl-3.0.txt] (see
-link:COPYING) or version 2 of the GNU General Public License
-{GPLv2}[http://www.gnu.org/licenses/gpl-2.0.txt] (see link:COPYING-GPL2).
+version 3.0 or later {LGPLv3+}[https://www.gnu.org/licenses/lgpl-3.0.txt]
+(see link:COPYING).
 
-The project leader {Eric Wong}[mailto:normalperson@yhbt.net] reserves
-the right to upgrade the project license to future versions of the LGPL
-(but no other licenses).
+It is also available under the GNU General Public License
+{GPLv2}[https://www.gnu.org/licenses/gpl-2.0.txt] (see link:COPYING-GPL2).
 
 Ruby posix_mq is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
 General Public License for more details.
 
 You should have received a copy of the GNU Lesser General Public License
-along with Ruby posix_mq; if not, write to the Free Software
-Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
+along with Ruby posix_mq; if not, see:
+https://www.gnu.org/licenses/lgpl-3.0.txt

posix_mq.gemspec

@@ -9,7 +9,6 @@ Gem::Specification.new do |s|
   s.name = %q{posix_mq}
   s.version = ENV["VERSION"].dup
   s.authors = ["Ruby POSIX MQ hackers"]
-  s.date = Time.now.utc.strftime('%Y-%m-%d')
   s.description = readme_description
   s.email = %q{ruby-posix-mq@bogomips.org}
   s.executables = %w(posix-mq-rb)
@@ -19,9 +18,8 @@ Gem::Specification.new do |s|
   s.homepage = Olddoc.config['rdoc_url']
   s.summary = summary
   s.rdoc_options = rdoc_options
-  s.rubyforge_project = %q{qrp}
   s.test_files = manifest.grep(%r{\Atest/test_.*\.rb\z})
   s.add_development_dependency(%q<olddoc>, "~> 1.0")
 
-  # s.licenses = %w(LGPLv3) # accessor not compatible with older RubyGems
+  s.licenses = %w(GPLv2 LGPLv3+)
 end