Perhaps solving the reserved filename problem at the Cygwin level would
be better than simply avoiding the reserved file names in the NetBSD
source tree.

As far as I know, the file system name space presented by Cygwin is
already somewhat different from that presented by the underlying host
OS.  For example, the directory that Cygwin calls "/bin" typically
matches the directory that the host OS calls "C:/cygwin/bin".

Since directory path mangling is already a part of Cygwin, perhaps it
would be easy to add reserved filename mangling to Cygwin.  For example,
insert an "x" at the beginning of every file name that matches the
regexp /^x*(nul|con|aux|prn|com[1-9]|lpt[1-9]).*/.  Then the files that
Cygwin calls "com1.c" and "xcom1.c" would match the files that the host
OS calls "xcom1.c" and "xxcom1.c".

--apb (Alan Barrett)