Do not use strncasecmp().  It is nonstandard and not portable.
Use Tcl_UtfNcasecmp() instead.
More ifdef shuffling: GETREADQUEUE and GETWRITEQEUE always defined,
dummy implementations return 0 if the requisite ioctls are not present.
TtyParseMode signature simplification: take single pointer to struct TtyAttrs 
instead of separate pointers to each member.