[m-rev.] for review: reword reference manual introduction

[Julien Fischer]

For review by anyone.

Reword reference manual introduction.

doc/reference_manual.texi:
    Reword the introduction: Mercury isn't new, it's over 20 years
    old at this point.

    Also, its current developers are no longer at the University
    of Melbourne.

Julien.

diff --git a/doc/reference_manual.texi b/doc/reference_manual.texi
index 5940aa57f..da3885401 100644
--- a/doc/reference_manual.texi
+++ b/doc/reference_manual.texi
@@ -120,7 +120,7 @@ into another language, under the above conditions for modified versions.
  @node Introduction
  @chapter Introduction

-Mercury is a new general-purpose programming language, designed
+Mercury is a general-purpose programming language, originally designed
  and implemented by a small group of researchers at the University
  of Melbourne, Australia.  Mercury is based on the paradigm of
  purely declarative programming, and was designed to be