doc/libNX_X11/lcUniConv: Pull over README from X.org's libX11 to document the…

doc/libNX_X11/lcUniConv/README

+
+The files in this directory are taken from the libiconv-1.1 package.
+
+The *.h files were generated from tables (mostly from ftp.unicode.org) using
+the programs '8bit_tab_to_h.c' and 'cjk_tab_to_h.c'. On some of them, further
+optimizations were applied by hand.
+
+If you find a bug in these files, instead of modifying them in XFree86
+and let it diverge from libiconv, please notify the libiconv maintainer
+(currently <bruno@clisp.org>) so he can fix both in synch.
+