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/asn1/test.asn1

@@ -7,6 +7,8 @@ BEGIN
 IMPORTS heim_any FROM heim;
 
 TESTuint32 ::= INTEGER (0..4294967295)
+TESTuint64 ::= INTEGER(0..18446744073709551615)
+TESTint64 ::= INTEGER(-9223372036854775808..9223372036854775807)
 
 TESTLargeTag ::= SEQUENCE {
 	foo[127] INTEGER (-2147483648..2147483647),