psl: add support for the [:*i..j] operator

This operator is to ':' what [*i..j] is to ';'.

Part of issue #51.

* doc/tl/tl.tex: Document syntax, semantic, and trivial
simplifications.
* doc/tl/spotltl.sty: Add macros for new operators.
* src/ltlast/bunop.cc, src/ltlast/bunop.hh: Implement it.
* src/ltlast/multop.cc: Add some trivial simplifications.
* src/ltlparse/ltlparse.yy, src/ltlparse/ltlscan.ll: Parse it.
* src/ltltest/equals.test, src/ltltest/latex.test,
src/tgbatest/ltl2tgba.test: Add more tests.
* src/ltlvisit/randomltl.cc: Output this operator in
random PSL formulas.
* src/ltltest/rand.test: Adjust.
* src/tgbaalgos/ltl2tgba_fm.cc: Add translation rules.
* src/ltlvisit/tostring.cc: Add pretty printing code.
* src/ltlvisit/simplify.cc, src/ltlvisit/snf.cc: Adjust
switches.
* NEWS: Mention the new operator.

NEWS

@@ -67,7 +67,14 @@ New in spot 1.99a (not yet released)
       either by Divine (as patched by the LTSmin people) or by
       Spins (the LTSmin compiler for Promela).
 
-    - LTL formulas can include /* comments */.
+    - LTL/PSL formulas can include /* comments */.
+
+    - PSL SEREs support a new operator [:*i..j], the iterated fusion.
+      [:*i..j] is to the fusion operator ':' what [*i..j] is to the
+      concatenation operator ';'.  For instance (a*;b)[:*3] is the
+      same as (a*;b):(a*;b):(a*;b).  The operator [:+], is syntactic
+      sugar for [:*1..], and corresponds to the operator ⊕ introduced
+      by Dax et al. (ATVA'09).
 
     - GraphViz output now uses an horizontal layout by default.
       The --dot option of the various command-line tools takes an