MEDIUM: applet: only keep appctx_new_*() and drop appctx_new()

This removes the mask-based variant so that from now on the low-level
function becomes appctx_new_on() and it takes either a thread number or
a negative value for "any thread". This way we can use task_new_on() and
task_new_anywhere() instead of task_new() which will soon disappear.
2 files changed