As of early 2013, the ICU project, maintained by IBM, is a pretty good answer to this.
http://site.icu-project.org/
ICU is a "complete, portable Unicode library that closely tracks industry standards." For the specific problem of string comparison, the Collation object does what you want.
The Mozilla Project adopted ICU for internationalization in Firefox in mid-2012; you can track the engineering discussion, including issues of build systems and data file size, here:
- https://groups.google.com/forum/#!topic/mozilla.dev.platform/sVVpS2sKODw
- https://bugzilla.mozilla.org/show_bug.cgi?id=724529 (tracker)
- https://bugzilla.mozilla.org/show_bug.cgi?id=724531 (build system)
