[patch, fortran, docs] Rewrite "GFortran and G77" section.

[Brooks Moses <brooks dot moses at codesourcery dot com>]

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2007-01-03  Brooks Moses  <brooks.moses@codesourcery.com>

	* gfortran.texi (GNU Fortran and G77): Rewrite

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This is a complete rewrite of the "GNU Fortran and G77" section of the 
introduction.  The original version was largely a justification for why 
we started from scratch rather than continuing to work with g77, which 
to me seems more relevant for the Wiki than the documentation.  This 
patch replaces it with a brief description of the fact that gfortran is 
the successor to g77 and should be essentially backwards-compatible with it.

My intention is to put an "Incompatibilities with G77" section in the 
language reference, to discuss the few things we do not intend to fix, 
and then put a link to that in this section as well.

Tested on trunk with "make pdf" and "make info".  Since this could 
potentially be controversial, I'll hold off for a couple of days before 
committing it under Steve's blanket approval, in case there are comments 
or disagreements.

- Brooks
Index: gfortran.texi
===================================================================
--- gfortran.texi	(revision 120428)
+++ gfortran.texi	(working copy)
@@ -391,38 +391,14 @@
 @cindex Fortran 77
 @cindex G77
 
-Why do we write a compiler front end from scratch? 
-There's a fine Fortran 77 compiler in the
-GNU Compiler Collection that accepts some features
-of the Fortran 90 standard as extensions.
-Why not start from there and revamp it?
+The GNU Fortran compiler is the successor to G77, the Fortran 77 front
+end included in GCC prior to version 4.  It is an entirely new program
+that has been designed to provide Fortran 95 support and extensibility
+for future Fortran language standards, as well as providing backwards
+compatibility for Fortran 77 and nearly all of the GNU language 
+extensions supported by G77.
 
-One of the reasons is that Craig Burley, the author of G77,
-has decided to stop working on the G77 front end.
-On @uref{http://world.std.com/~burley/g77-why.html,
-Craig explains the reasons for his decision to stop working on G77}
-in one of the pages in his homepage.
-Among the reasons is a lack of interest in improvements to
-@command{g77}.
-Users appear to be quite satisfied with @command{g77} as it is.
-While @command{g77} is still being maintained (by Toon Moene),
-it is unlikely that sufficient people will be willing
-to completely rewrite the existing code. 
 
-But there are other reasons to start from scratch.
-Many people, including Craig Burley,
-no longer agreed with certain design decisions in the G77 front end.
-Also, the interface of @command{g77} to the back end is written in
-a style which is confusing and not up to date on recommended practice.
-In fact, a full rewrite had already been planned for GCC 3.0.
-
-When Craig decided to stop,
-it just seemed to be a better idea to start a new project from scratch,
-because it was expected to be easier to maintain code we
-develop ourselves than to do a major overhaul of @command{g77} first,
-and then build a Fortran 95 compiler out of it.
-
-
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