Ruby 2.0 support

Ruby 2.0 has a few new RbConfig variables, {ruby,vendor,site}archhdrdir.
At least rubyarchhdrdir needs to be used to correctly locate
ruby/config.h, since it is architecture specific.

The attached patch adapts configure.ac to recognize ruby2.0/rdoc2.0 and
swig.m4 to use rubyarchhdrdir if it's available.

There's some additional work that may be needed in
build/ac-macros/swig.m4 and tools/dev/unix-build/Makefile.svn, as
sitearchdir isn't necessarily a subset of sitedir for ruby >=2.0.

$ ruby1.9.1 -rrbconfig -e 'puts RbConfig::CONFIG["sitearchdir"]'
/usr/local/lib/site_ruby/1.9.1/x86_64-linux

$ ruby1.9.1 -rrbconfig -e 'puts RbConfig::CONFIG["sitedir"]'
/usr/local/lib/site_ruby

$ ruby2.0 -rrbconfig -e 'puts RbConfig::CONFIG["sitearchdir"]'
/usr/local/lib/x86_64-linux-gnu/site_ruby

$ ruby2.0 -rrbconfig -e 'puts RbConfig::CONFIG["sitedir"]'
/usr/local/lib/site_ruby

Cheers,

-- 
James
GPG Key: 4096R/331BA3DB 2011-12-05 James McCoy <jamessan_at_debian.org>