Modules in Cygwin are sorta like modules in Bionic; fixed.
Added workaround for FD_ISSET bug in Cygwin (demotion of long to int) for mux.
Added workarounds to module and path for Cygwin to accomodate Windows ".dll" versus Linux ".so".
Fixed bug in tree unit test.

git-svn-id: svn://graphite/diminuto/trunk@577 5dfbf39a-1452-0410-8a97-9e58fedde8e3