Adopt a newer condition on post-call sequence point insertion.

From upstream commit 488888ce612491aca1c97f79ddbad685302d43cc.
When single stepping from a exception throw site, single step to the catch site. Fixes #652590.
Emit a seq_point after OP_START_HANDLER, not before.
Avoid putting a seq point at the beginning of finally clauses, they already have one. Fixes #686269.
Emit a seq point for endfinally opcodes even if the stack is not empty. Fixes #6864.
Ignore requests to set breakpoints at il offsets belonging to dead code. Fixes #11880.