Class members now loaded on-demand.

This saves a very small amount of memory now, since str's concat and list's
size only have vars made for them if they are used somewhere. I'm hoping this
will end up saving a great deal more memory in the future.

This required juggling around lily_func_seed, which now has a ->next that is
const.

Seeds for str and list are now static const. Hopefully that will result in
some memory saving too.

lily_pkg.h is now gone, with lily_func_seed having found its way into
lily_syminfo.h with everything else.

This comes at the cost of needing to pass the symtab to do class member
lookups now. However, making lookups automatically do the load means that
there won't be some future bug of "suchandsuch doesn't do autoloading".