Alpha equiv 2 - Electric Boogaloo

[leissa]

Alpha-Equivalence checks now knows two modes:

• In infer mode, type inference is happening and Infer%s will be resolved, if possible.
  Also, two free but different Var%s are considered α-equivalent.
• When *not in infer mode, no type inference is happening and Infer%s will not be touched.
  Also, Two free but different Var%s are not considered α-equivalent.

In addition:

• tuples/sigma are now converted to packs/arrs modulo α-equivalence:
  • (a, a') => ‹2; a›
  • [A, A'] => «2; A»
• fixes Performance depends on the size of Arr/pack #109
• should also fix the related issue in Start working on a RegEx dialect as a normalization showcase. #210

[fodinabor]

Jup, this correctly types the (f, (ff, t)#done)#matched arg thing, so one can call it.

(Backend still doesn't like these things ^^)