Add FILE_LICENCE declarations to almost all files that make up the
various standard builds of gPXE.

attempt at triggering TCP-related protocols to start).

ensure that we only drop our self-reference exactly once.

To maintain the guarantee that an object won't go out of scope
unexpectedly while one of its event handlers is being called, the
event-calling functions now automatically obtain and drop extra
references.

functions.

Add "xfer" to all xfer functions and "job" to all job functions.

in code defining reference-counted objects.