Crypto endpoint relation compare routines cleanup

* Trying not to assume an int is at least 32 bits.

* Technically speaking, comparing "unrelated" addresses is undefined
  behaviour which can be avoided by a cast to uintptr_t.

* The early out if either local_crypto == 0 does work in context,
  provided the nodes in tree never have local_crypto == 0.  That implies
  crypto_insert_endpoint_relation must never have a 0 in there, which I
  think the callers do respect.  Still I think it is better to not hide
  these assumptions in the compare function and address the problem in
  the lookup function instead.

These changes likely make the code fractionally slower, but I do think
they improve clarity.

Signed-off-by: Erik Boasson <eb@ilities.com>

src/security/core/tests/secure_communication.c

@@ -544,7 +544,7 @@ CU_TheoryDataPoints(ddssec_secure_communication, multiple_readers) = {
     CU_DataPoints(size_t, 1, 3, 1, 3), /* number of participants per domain */
     CU_DataPoints(size_t, 3, 1, 3, 3), /* number of readers per participant */
 };
-CU_Theory((size_t n_dom, size_t n_pp, size_t n_rd), ddssec_secure_communication, multiple_readers, .timeout = 60, .disabled = false)
+CU_Theory((size_t n_dom, size_t n_pp, size_t n_rd), ddssec_secure_communication, multiple_readers, .timeout = 90, .disabled = false)
 {
   DDS_Security_ProtectionKind metadata_pk[] = { PK_N, PK_SOA, PK_EOA };
   DDS_Security_BasicProtectionKind payload_pk[] = { BPK_N, BPK_S, BPK_E };