config: Slightly neater configuration table size macros

config: Slightly neater configuration table size macros

Macro SHP_TYPE_MAX is the largest possible ship type number.  It is
only used to size mchr[], and we need + 2 there.  Replace by MCHR_SZ
for simplicity.

Same for LND_TYPE_MAX, PLN_TYPE_MAX, P_MAX, and SCT_TYPE_MAX: replace
by LCHR_SZ, PLCHR_SZ, PCHR_SZ, and DCHR_SZ.

Same for N_MAXNUKE, except that one is more than the largest type
number.  Replace by NCHR_SZ.

For consistency, define ICHR_SZ and INTRCHR_SZ for sizing ichr[] and
intrchr_sz[].

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>