Remove consumeexact & constrainingARPs

[tschoesi]

Silicon contains some code related to the fresh statement that according to @mschwerhoff is not needed anymore and could be removed See for example here and Silver Issue 87.

[mschwerhoff]

Corrections:

• State entry constrainingARPs is currently still used to record currently constrainable wildcards, e.g. for fold P(x), where P's body contains a wildcard. The state entry should be renamed for clarity, however.
• Assuming that wildcard is not allowed in compound expressions such as 2*wildcard or 1/2+wildcard, then it should be possible to simplify def consumeExactRead by removing all corresponding cases