tools: Add a --format option

* src/bin/common_output.cc: Add option --format and implement
it.
* src/bin/ltlfilt.cc, src/bin/randltl.cc: Document the
supported %-sequences.
* src/bin/genltl.cc: Document the %-sequences, and supply
the name of the pattern to output_formula().
* doc/org/genltl.org, doc/org/ioltl.org, doc/org/ltlfilt.org,
NEWS: Document it.
* src/ltltest/latex.test: Use it.

doc/org/ltlfilt.org

@@ -253,6 +253,23 @@ It is therefore equivalent, but that is not a surprise since the
 [[http://homepages.inf.ed.ac.uk/kousha/note_on_stut_tl_lpi.ps][this procedure]] (calling the =remove_x()= function, and building automata
 to check the equivalence of the resulting formula with the original one).
 
+* Using =--format=
+
+The =--format= option can be used the alter the way formulas are output (for instance use
+#+HTML: <code>--latex --format='$%f$'</code>
+to enclose formula in LaTeX format with =$...$=).  You may also find
+=--format= useful in more complex scenarios.  For instance you could
+print the only the line numbers containing formulas matching some
+criterion.  In the following, we print only the numbers of the lines
+of =scheck.ltl= that contain guarantee formulas:
+
+#+BEGIN_SRC sh :results verbatim :exports both
+ltlfilt --lbt-input -F scheck.ltl --guarantee --format=%L
+#+END_SRC
+#+RESULTS:
+: 2
+: 3
+: 4
 
 #  LocalWords:  ltlfilt num toc LTL PSL syntaxes LBT's SRC GFp scheck
 #  LocalWords:  ltl EOF lbt Gp Fp Xp XFp XXp randltl ary nnf wm abc