[Doc/Eva] major update to the Eva tutorial; documentation improvements

doc/userman/userman.bib

 @manual{plugin-dev-guide,
-  author = {Julien Signoles and Loïc Correnson and Matthieu Lemerre and 
+  author = {Julien Signoles and Thibaud Antignac and Loïc Correnson and Matthieu Lemerre and
             Virgile Prevosto},
   title  = {{Frama-C Plug-in Development Guide}},
   year   = 2015,

doc/value/biblio.bib

@@ -73,6 +73,14 @@
   organization = {CEA, List},
   note =      {Available at \url{https://frama-c.com/download/frama-c-user-manual.pdf}}}
 
+@manual{plugin-dev-guide,
+  author = {Julien Signoles and Thibaud Antignac and Loïc Correnson and Matthieu Lemerre and
+            Virgile Prevosto},
+  title  = {{Frama-C Plug-in Development Guide}},
+  year   = 2015,
+  month  = feb,
+  note   = {\newline \url{http://frama-c.com/download/frama-c-plugin-development-guide.pdf}},
+}
 
 @inproceedings{DBLP:conf/sas/JacqueminPV18,
   author    = {Maxime Jacquemin and

doc/value/gui.tex

@@ -21,7 +21,7 @@ As a general recommendation,
   \Eva{} does not use the GUI for anything else other than rendering its
   results. It is recommended to run the value analysis using the command line,
   and then saving the result to a Frama-C save file
-  (see Section~\ref{saving-result}).
+  (see Section~\ref{three-step}).
 
 \section{A general view of the GUI}
 

doc/value/tutorial/main_1.c

 #include "skein.h"
+#include <stdio.h>
 
 #define HASHLEN (8)
 
-int printf(const char*,...);
-
 u08b_t msg[80]="People of Earth, your attention, please";
 
 int main(void)
 {
   u08b_t hash[HASHLEN];
   int i;
-  Skein_256_Ctxt_t skein_context; 
+  Skein_256_Ctxt_t skein_context;
   Skein_256_Init( &skein_context, HASHLEN);
   Skein_256_Update( &skein_context, msg, 80);
   Skein_256_Final( &skein_context, hash);