Rename README.txt to README.rst and convert to reStructuredText
diff --git a/vncviewer/vncviewer.cxx b/vncviewer/vncviewer.cxx
index bd3a562..d15a804 100644
--- a/vncviewer/vncviewer.cxx
+++ b/vncviewer/vncviewer.cxx
@@ -99,7 +99,7 @@
   snprintf(buffer, sizeof(buffer),
            _("TigerVNC Viewer %d-bit v%s\n"
              "Built on: %s\n"
-             "Copyright (C) 1999-%d TigerVNC Team and many others (see README.txt)\n"
+             "Copyright (C) 1999-%d TigerVNC Team and many others (see README.rst)\n"
              "See http://www.tigervnc.org for information on TigerVNC."),
            (int)sizeof(size_t)*8, PACKAGE_VERSION,
            BUILD_TIMESTAMP, 2017);