nyacc: Add README.nyacc.

* README.nyacc: New file.

README.nyacc

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+This is a version 0.72.0 of NYACC (Not Yet Another Compiler Compiler!).
+
+Copyright (C) 2015,2016 Matthew R. Wette
+
+Copying and distribution of this file, with or without modification,
+are permitted in any medium without royalty provided the copyright
+notice and this notice are preserved.  This file is offered as-is,
+without any warranty.
+
+This software package is covered by the following licenses:
+* GNU PUBLIC GENERAL LICENCE, version 3 (See COPYING.)
+* GNU LESSER PUBLIC GENERAL LICENCE, version 3 (See COPYING.LESSER.)
+* GNU Free Documentation License, version 1.3 (See doc/nyacc/COPYING.DOC.)
+
+There is an incomplete manual in doc/nyacc/.
+
+There is a demo program calc.scm in examples/nyacc/lang/calc.  Easy starter:
+  $ cd examples/nyacc/lang/calc
+  $ ./calc
+  2 + 2 => 4
+
+The module code is in module/nyacc.  Modules are imported as follows:
+  (use-modules (nyacc lalr))
+  (use-modules (nyacc lex))
+
+If you have a personal guile directory then you can copy modules/nyacc
+to that directory.  To install in the global guile distribution:
+  user$ sudo -s 
+  root# cd module
+  root# make -f Makefile.nyacc install
+  root# exit
+  user$
+
+The syntax and nomenclature should be considered not stable.
+