update some URLs to skip permanent redirections

* doc/org/concepts.org, doc/org/ltlcross.org, doc/org/ltldo.org,
python/ajax/trans.html, tools/man2html.pl: Update URLs.

doc/org/concepts.org

@@ -54,7 +54,7 @@ Andersen's lecture notes]].
 
 In Spot, BDDs are one way to represent Boolean formulas, and in
 particular, they are used to labels the edges of [[#buchi][automata]]. Spot uses a
-customized version of [[http://sourceforge.net/projects/buddy/][the BuDDy library]] for manipulating BDDs.
+customized version of [[https://sourceforge.net/projects/buddy/][the BuDDy library]] for manipulating BDDs.
 
 * ω-word
    :PROPERTIES:

doc/org/ltlcross.org

@@ -101,7 +101,7 @@ No problem detected.
 =ltlcross= can only read four kinds of output:
   - Never claims (only if they are restricted to representing an
     automaton using =if=, =goto=, and =skip= statements) such as those
-    output by [[http://spinroot.com/][=spin=]], [[http://www.lsv.ens-cachan.fr/~gastin/ltl2ba/][=ltl2ba=]], [[http://sourceforge.net/projects/ltl3ba/][=ltl3ba=]], or =ltl2tgba --spin=.  The
+    output by [[http://spinroot.com/][=spin=]], [[http://www.lsv.ens-cachan.fr/~gastin/ltl2ba/][=ltl2ba=]], [[https://sourceforge.net/projects/ltl3ba/][=ltl3ba=]], or =ltl2tgba --spin=.  The
     newer syntax introduced by Spin 6.24, using =do= instead of =if=,
     is also supported.
   - [[http://www.tcs.hut.fi/Software/lbtt/doc/html/Format-for-automata.html][LBTT's format]], which supports generalized Büchi automata with

doc/org/ltldo.org

@@ -19,7 +19,7 @@ any other tool.
 * Example: computing statistics for =ltl3ba=
 
 As a motivating example, consider a scenario where we want to run
-[[http://sourceforge.net/projects/ltl3ba/][=ltl3ba=]] on a set of 10 formulas stored in a file.  For each formula
+[[https://sourceforge.net/projects/ltl3ba/][=ltl3ba=]] on a set of 10 formulas stored in a file.  For each formula
 we would like to compute compute the number of states and edges in the
 Büchi automaton produced by =ltl3ba=.