heimdal: asn1: Use unsigned bitfields for named bitsets

heimdal: asn1: Use unsigned bitfields for named bitsets

Import upstream 6747e1628:

  asn1: Use unsigned bitfields for named bitsets

  Signed 1-bit bitfields are undefined in C.

This should fix the following warnings, which for unknown reasons are
errors in CI:

  /usr/src/crypto/heimdal/lib/hx509/ca.c:1020:22: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
   1020 |         ku.digitalSignature = 1;
        |                             ^ ~
  /usr/src/crypto/heimdal/lib/hx509/ca.c:1021:21: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
   1021 |         ku.keyEncipherment = 1;
        |                            ^ ~
  /usr/src/crypto/heimdal/lib/hx509/ca.c:1028:17: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
   1028 |         ku.keyCertSign = 1;
        |                        ^ ~
  /usr/src/crypto/heimdal/lib/hx509/ca.c:1029:13: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
   1029 |         ku.cRLSign = 1;
        |                    ^ ~

PR:		276960
Fixes:		1b7487592987
MFC after:	1 week