Simplify storage of orphan transactions

Orphan transactions were stored as a CDataStream pointer;
this changes the mapOrphanTransactions data structures to
store orphans as a CTransaction.

This also fixes CVE-2013-4627 by always re-serializing
transactions before relaying them.
Make RPC password resistant to timing attacks

Fixes issue#2838; this is a tweaked version of pull#2845 that
should not leak the length of the password and is more generic,
in case we run into other situations where we need
timing-attack-resistant comparisons.
Performance optimization for bloom filters.

This reduces a peer's ability to attack network resources by
 using a full bloom filter, but without reducing the usability
 of bloom filters.  It sets a default match everything filter
 for peers and it generalizes a prior optimization to
 cover more cases.
Merge pull request #5 from Fantu/security-fixes

Security fixes