Use Bundler::GemHelper.gemspec instead of loading it
Bump rake-compiler to 0.9
Change cross host from i686-w64-mingw32 to x86_64-w64-mingw32

Not sure if this is just different on Fedora or if it changed. May need
to have dynamic detection using `RbConfig::CONFIG['host_cpu']` in the
future.
Update bundled taglib for cross to 1.9.1

Also update download URL, which seems to have changed.