CygWin/gcc-3.4.4 updates. I replaced my cygwin compiler with 3.4.4, did a make clean of plib, simgear, and flightgear, then did a make install of all three. With the included changes, everything builds fine, and runs fine.
"#include <simgear/compiler.h>".
DOCS/README.layout in the base package for details, along with the modified dialog files.