add enviroment variables for FORQ algorithm

* AUTHORS: added Jonah Romero
* bin/man/spot-x.x: Added the enviroment variables,
                    SPOT_EXCLUSIVE_WORD and SPOT_CONTAINMENT_CHECK
* doc/spot.bib: Added paper citation for FORQ inclusion algorithm
* spot/twa/twa.cc: Modified exclusive_word to also use FORQ
* spot/twaalgos/contains.cc: Modified contains to also use FORQ

doc/spot.bib

@@ -336,6 +336,19 @@
   month		= aug
 }
 
+@inproceedings{doveriFORQBasedLanguageInclusion2022,
+  title = {{{FORQ-Based Language Inclusion Formal Testing}}},
+  booktitle = {{{CAV}}'22: {{Proc}}. 32nd {{Int}}. {{Conf}}. on {{Computer Aided Verification}}},
+  author = {Doveri, Kyveli and Ganty, Pierre and Mazzocchi, Nicolas},
+  year = {2022},
+  volume = {13372},
+  pages = {109--129},
+  publisher = {{Springer International Publishing}},
+  doi = {10.1007/978-3-031-13188-2_6},
+  urldate = {2022-09-15},
+  isbn = {978-3-031-13187-5 978-3-031-13188-2}
+}
+
 @InProceedings{	  duret.11.vecos,
   author	= {Alexandre Duret-Lutz},
   title		= {{LTL} Translation Improvements in {Spot}},