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[TESTS][LAMBDA] Improved pp_lambda; update a test

- redifine sigma (Value.sigma and Lamda.sigma)
- add sigma application in eval
- fix typing rules for abstraction and match
- XXX This commit breaks all tests !!!

* More agressive simplifications of unused variables, and variable beautification of remaining variable (i.e.
rename _fresh_xxx, _fresh_yyy into $A, $B, ...

	add operator "=" for integers;
	add constant values "`true" and "`false" as possible patterns