Convert README, INSTALL, and CHANGES to markdown.

INSTALL → INSTALL.md

-
-                  Installation instructions
+Installation instructions
+=========================
 
 
 Installation from a source distribution (tarball)
@@ -7,14 +7,14 @@ Installation from a source distribution (tarball)
 
 After unpacking, installation is done by
 
-  ./configure
-  make
-  make install (as root)
+    ./configure
+    make
+    make install (as root)
 
-To install also the Ocaml library do
+To install also the Ocaml library, do
 
-  make byte
-  make install-lib (as root)
+    make byte
+    make install-lib (as root)
 
 
 Installation from the git repository
@@ -22,15 +22,16 @@ Installation from the git repository
 
 First run
 
-      autoconf
-      automake --add-missing
+    autoconf
+    automake --add-missing
 
-to build the ./configure file and install the helper scripts, then follow
-instructions from the section above.
+to build the `./configure` file and install the helper scripts, then follow
+the instructions from the section above.
 
 
 Detailed instructions
 ---------------------
 
 For detailed instructions and required dependencies, please see
-the manual (doc/manual.pdf), Chapter 5 "Compilation, Installation".
+the manual [doc/manual.pdf](http://why3.lri.fr/manual.pdf), Chapter 5
+[Compilation, Installation](http://why3.lri.fr/doc/install.html).

README → README.md

+WHY 3
+=====
 
 Why3 is a platform for deductive program verification. It provides
 a rich language for specification and programming, called WhyML, and
@@ -11,42 +13,43 @@ automated extraction mechanism. WhyML is also used as an intermediate
 language for the verification of C, Java, or Ada programs.
 
 PROJECT HOME
-============
+------------
 
-http://why3.lri.fr
+http://why3.lri.fr/
 
-https://gforge.inria.fr/projects/why3
+https://gitlab.inria.fr/why3/why3
 
 DOCUMENTATION
-=============
+-------------
 
-The documentation (a tutorial and a reference manual) is in
-the file doc/manual.pdf.
+The documentation (a tutorial and a reference manual) is in the file
+[doc/manual.pdf](http://why3.lri.fr/manual.pdf) or online at
+http://why3.lri.fr/doc/.
 
-Various examples can be found in the subdirectories theories/
-and examples/.
+Various examples can be found in the subdirectories [theories/](theories)
+and [examples/](examples).
 
 Mailing list (Why3 Club):
   http://lists.gforge.inria.fr/mailman/listinfo/why3-club
 
 Bug Tracking System:
-  https://gforge.inria.fr/tracker/?atid=10293&group_id=2990&func=browse
+  https://gitlab.inria.fr/why3/why3/issues
 
 COPYRIGHT
-=========
+---------
 
 This program is distributed under the GNU LGPL 2.1. See the enclosed
-file LICENSE.
+file [LICENSE](LICENSE).
 
-The files src/util/extmap.ml{i} are derived from the sources of
-OCaml 3.12 standard library, and are distributed under the GNU
-LGPL version 2 (see file OCAML-LICENSE).
+The files [src/util/extmap.ml{i}](src/util/extmap.mli) are derived from the
+sources of OCaml 3.12 standard library, and are distributed under the GNU
+LGPL version 2 (see file [OCAML-LICENSE](OCAML-LICENSE)).
 
 Icon sets for the graphical interface of Why3 are subject to specific
 licenses, some of them may forbid commercial usage. These specific
-licenses are detailed in files share/images/*/*.txt
+licenses are detailed in files [share/images/\*/\*.txt](share/images).
 
 INSTALLATION
-============
+------------
 
-See the file INSTALL.
+See the file [INSTALL.md](INSTALL.md).