Cleanup and orginization of various bits of code

array.c/h:
        factored array_map into c_array_map,array_map, and array_nmap
        copied a bunch of function declarations into array.h that had
               had been in array.c a while
added conditions.c and sequences.c

common.h:
        refactored constructors into a set of macros instead of using
                   literal sexps
hash.c/h:
        got everything to compile, still need to implement hash_delete
cons.c:
        rewrote the c make list functions, added a couple of cons_sexp
                macro calls in place of literal values
prim.c/lisp_math.c/h
        moved mod from prim.c to lisp_math.c, I intend to move some more
              math functions sooner or later
sequence.c/h:
        added sequence.c and moved length into sequence.c from prim.c