Disallow break or continue across a function boundary

Code containing breaks or continues that attempt to jump across a
function boundary weren't detected during analysis but would crash
the compiler during code generation. Add diagnostics for these kinds
of errors.

Example:

fun f() {
    while (true) {
        fun inner() {
            continue
        }
    }
}

 #KT-4334 Fixed
Merge pull request #388 from dezgeg/fix-jump-across-function-boundary

KT-4334: Disallow break or continue across a function boundary