When generating a dynamic method both with many unconditional jumps, the
ILGenerator's computation of maxstack is way to large - it adds the max
stack of each basic block ending with an unconditional transfer
(br, ret, throw, etc). If the generated code has many such bbs
(eg, from the "then" clauses of if-then-else constructs) this sum can
overflow 2^16. When it does, the maxstack recorded/used is the computed
value mod 2^16. When that is less than the correct value, the
JIT throws an InvalidProgramException.

Keep track of the stack depth at various positions and use it to
calculate an adjustment to the depth.

Fix dotnet#63805