Address a compiler error on illumos.

Apparently, in this context UINT_MAX happens to be defined on all OSes
currently in CI except illumos (both GCC and Clang):

gcc (OmniOS 151044/12.2.0-il-0) 12.2.0:
print-snmp.c:543:48: error: 'UINT_MAX' undeclared (first use in this
  function)
print-snmp.c:276:1: note: 'UINT_MAX' is defined in header '<limits.h>';
  did you forget to '#include <limits.h>'?

Instead of including <limits.h> (which indeed would define the constant)
match the variable type by using UINT32_MAX, which happens to be defined
already.

print-snmp.c

@@ -540,7 +540,7 @@ asn1_parse(netdissect_options *ndo,
 					goto invalid;
 				}
 				if (GET_U_1(p) & ASN_BIT8)	/* negative */
-					data = UINT_MAX;
+					data = UINT32_MAX;
 				for (i = elem->asnlen; i != 0; p++, i--)
 					data = (data << ASN_SHIFT8) | GET_U_1(p);
 				elem->data.integer = data;