Make the compiler stop generating JumpPtr instructions

The only case where it did so was for a tail call. This can use a Return
instruction instead, with what looks like no additional overhead.

(Proofs not updated in this commit.)
fix toBytecodeProofsTheory for new tail call code

The proof scripts actually go through exactly the same. The only change
was the sequence of bytecode instructions that "jmpbc" abbreviates.
delete JumpPtr from bytecode semantics

(proofs not updated)
fix bytecode proofs for removed JumpPtr
Merge remote-tracking branch 'origin/remove-JumpPtr'