fp/secd: compiler preliminaries

1)  This commit can compile (tests/append.scm -> tests/append.secd)
a simple recursion into SECD codes

    $ mzscheme -f eval.scm < tests/append.scm 2>/dev/null >tests/append.secd

produces a list of SECD commands which can be run on the machine:
    $ ./secd < tests/append.secd

Or:
    $ mzscheme -f eval.scm <tests/append.scm 2>/dev/null | ./secd

2) Executable files format now requires the toplevel list paenthesis:

    $ echo "(LDC 2 LDC 2 ADD)" | ./secd
    4

3) .secd files moved to tests/

4) Fixed small bugs in CONS code generation and secd.c:list_eq()