These functions are used to compose a vw_handler object into
text that will be interpreted either as a complete JavaScript
function, or a function-body.
vw_handler_body_compose(vw_handler, n_indent = 2L)
vw_handler_compose(vw_handler)vw_handler created using vw_handler_signal() or
vw_handler_event()
integer, number of spaces to indent the text of the body
object with S3 class JS_EVAL, text for the function or
function-body