gh-126211: Exclude preprocessor directives from statements containing escaping calls...

gh-126211: Exclude preprocessor directives from statements containing escaping calls (#126213)

The cases generator inserts code to save and restore the stack pointer around
statements that contain escaping calls. To find the beginning of such statements,
we would walk backwards from the escaping call until we encountered a token that
was treated as a statement terminator. This set of terminators should include
preprocessor directives.