(max_pop): Use it. Don't support null argument anymore.
(nati, gen_power): Use max_population() instead of max_pop() with null
argument.
(show_sect_stats): Use max_population() to simplify the code.
(prod, upd_buildeff): Use max_population() to get correct new maximum
population for limiting work when tearing down a big city.
Previously, this was broken in upd_buildeff(). In prod(), it was
broken when the new designation had odd maximum population, which
should not occur.
instead of declaring them all over the place. This uncovered type
errors:
(s_p_etu, adj_update): Defined long, sometimes declared int. Kills
big endian machines where sizeof(long) != sizeof(int). Change to
int.
(set_option, delete_option, optstrset, intset, floatset, doubleset,
longset, optionset, optiondel, worldxset): Change linkage to static.
effect. Replace calls by struct assignment where possible. Replace
clear buffer, copy string to buffer by strncpy(). Use assignment to
clear when that's clearer. Replace overlapping copy through bounce
buffer by memmove(). Replace rest by standard memset() and memcpy().
Also use sizeof() instead of literal array sizes for robustness, and
instead of symbolic array sizes for clarity.
