* Complete redesign of the operating-system interface. I/O is more

* Complete redesign of the operating-system interface.  I/O is more
uniform and is able to take advantage of things like sockets, pipes,
ptys, etc.  All I/O buffering is moved into the runtime system for
better performance with Scheme compiler code.  Strong knowledge of
POSIX.1 should make porting to VMS easy once VMS supports POSIX.1.

* Change operating system conditionalizations to standard form
suggested by POSIX.1.

* Add FSF macros to support ANSI declarations.

* Add dynamic-stack package and obstacks.

* Provide higher-level utilities for parsing command line options.

* Instead of `Back_To_Eval', there is now a procedure
`abort_to_interpreter' which knows about everything that needs to be
cleaned up.

* Change names of some macros:

	Pop				STACK_POP
	Push				STACK_PUSH
	Push_From			STACK_LOCATIVE_PUSH
	Pop_Into			STACK_LOCATIVE_POP (similar)
	Stack_Ref			STACK_REF
	Top_Of_Stack()			STACK_REF(0)
	Simulate_Popping		STACK_LOC
	Simulate_Pushing		STACK_LOC (similar)
	Stack_Distance			STACK_LOCATIVE_DIFFERENCE (similar)
	Pop_Primitive_Frame		POP_PRIMITIVE_FRAME
	Metering_Apply_Primitive	PRIMITIVE_APPLY
	Export_Regs_Before_Primitive	EXPORT_REGS_BEFORE_PRIMITIVE
	Import_Regs_After_Primitive	IMPORT_REGS_AFTER_PRIMITIVE

* Sun assembler can't handle a constant used in "cmpaux-mc68k.m4", so
provide an option to rewrite that instruction as two instructions.

* Some compilers won't cast a function to an integer, so kludge around
it by mis-declaring the external function as an integer, taking it the
integer's address, and casting THAT to an integer.

* Move critical section code and termination code to their own files.