some sys/windows build updates

Place built libraries for Lua and pdcurses into lib instead of the
more transient src/o subfolder.

Remove a kludge involving sys/windows/stub-pdcscrn.c.

Don't link pdcurses into NetHackW.exe (required a couple of stubs
since NetHack.exe and NetHackW.exe currently share object files
under the visual studio nmake build.

(Note: This may require a couple of follow-on minor modifications
to the mingw build. If so, the CI will flag that for us after this
commit)

sys/windows/stubs.c

@@ -198,4 +198,23 @@ set_keyhandling_via_option(void)
 {
     return 1;
 }
+
+#ifdef CURSES_GRAPHICS
+struct window_procs curses_procs = {0};
+
+int curses_read_attrs(const char *attrs)
+{
+    return 0;
+}
+
+char *
+curses_fmt_attrs(char *outbuf)
+{
+    int attr = iflags.wc2_petattr;
+    outbuf[0] = '\0';
+    Sprintf(outbuf, "+unknown [%d]", attr);
+    return &outbuf[1];
+}
+#endif
+
 #endif /* TTYSTUBS */