Add 64-bit integer support to ASN.1 compiler

ASN.1 INTEGERs will now compile to C int64_t or uint64_t, depending
    on whether the constraint ranges include numbers that cannot be
    represented in 32-bit ints and whether they include negative
    numbers.

    Template backend support included.  check-template is now built with
    --template, so we know we're testing it.

    Tests included.

lib/hdb/hdb.asn1

@@ -118,6 +118,7 @@ HDB-extension ::= SEQUENCE {
 		hist-kvno-diff-clnt[10]		INTEGER (0..4294967295),
 		hist-kvno-diff-svc[11]		INTEGER (0..4294967295),
 	        policy[12]			UTF8String,
+		principal-id[13]		INTEGER(-9223372036854775808..9223372036854775807),
 		...
 	},
 	...