according to context, to make `lstat * ?type#spy&spy>1' work. Closes
bug#825363, #905809, #905814 and #922968.
(nsc_type, packed_nsc_type, nsc_cat, packed_nsc_cat, nsc_flags): New.
(valstr): New. Old code encoded values in type long, which was
somewhat hard to read and could only support signed integer values.
(nscstr): Redesign. Use valstr. Typed operator.
(castr): Split ca_code into ca_type, ca_flags, ca_off. Tables
changed.
(nstr_comp, nstr_exec): Redesign and rewrite. Callers changed. They
used the old design incorrectly, which let players smash the stack
by supplying more than NCOND conditions.
(encode, nstr_comp_val, decode, nstr_exec_val): Rename, redesign, and
rewrite. Callers changed.
(nstr_coerce_val): New.
(var_ca, sect_ca, ship_ca, land_ca): Checking both var_ca[] and the
object's ca complicates proper recognition of unique abbreviations.
Copy contents of var_ca[] into the ca of objects, remove var_ca[].
(surv): Reject values with category other than NSC_OFF and types that
can't be coerced to NSC_LONG. Old code happily passed values with
category NSC_VAL to code_char(). The previous version interpreted
them correctly, but earlier versions interpreted them as NSC_OFF, then
logged `bad type in decode: 0' and evaluated them into zero.
(code_char): Used to test category NSC_VAR to decide whether to
display tens or hundreds. NSC_VAR no longer exists. Test type
instead. Makes more sense anyway.
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.
