Log Message:
Update to 2.4

* Improve cygwin packaging. (Phil Nelson)
* Avoid infinite loop when a configure test fails. (Christer Bernerus)
* Increase minimal LWP stack size to 32KB. (Christer Bernerus)
* Add pkgconfig file.
* Do not require an executable stack.
* Cancel pending IOMGR requests when a thread dies.