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

the assert message's file and line number gives some clue as to the
real location of the problem.

Added similar assertions to list.h.

the assert message's file and line number gives some clue as to the
real location of the problem.

Added similar assertions to list.h.

those functions we are likely to need.

Still need to come up with a way of getting the linker to create
static lists using this linking mechanism.