[Wallet] Improve ReorderTransactions(..)
[Qt] Call checkBalanceChanged() periodically instead for every updated transaction
Combine CCoinsViewCache's HaveCoins and const GetCoins into AccessCoins.

The efficient version of CCoinsViewCache::GetCoins only works for known-to-exist
cache entries, requiring a separate HaveCoins call beforehand. This is
inefficient as both perform a hashtable lookup.

Replace the non-mutable GetCoins with AccessCoins, which returns a potentially-NULL
pointer. This also decreases the overloading of GetCoins.

Also replace some copying (inefficient) GetCoins calls with equivalent AccessCoins,
decreasing the copying.
Add testnet DNS seed of Andreas Schildbach.

It runs sipas crawler, but rather than using its custom nameserver implementation it serves a generated zonefile via bind9. The zone always contains 25 IPv4 and 25 IPv6 peers. FWIW, the zone is secured using DNSSEC.
Clarify 'compressed nor uncompressed' error message
Merge pull request #4862

45a4baf Add testnet DNS seed of Andreas Schildbach. (Andreas Schildbach)
Merge pull request #4697

da2ede2 [Wallet] Improve ReorderTransactions(..) (Cozz Lovan)
Merge pull request #4712

80daee0 [Qt] Call checkBalanceChanged() periodically instead for every updated transaction (Cozz Lovan)
netbase: Use .data() instead of .c_str() on binary string

`.c_str()` is only guaranteed to return the data up to the first NUL
character.
Merge pull request #4865

8e44f2e Clarify 'compressed nor uncompressed' error message (Peter Todd)
Avoid repeated lookups in mapOrphanTransactions and mapOrphanTransactionsByPrev
Rename script.h/.cpp to scriptutils.h/.cpp (plus remove duplicated includes)
Move CScript class and dependencies to script/script
Separate script/interpreter
Separate script/standard
Separate CScriptCompressor
Separate script/sign
Merge pull request #4754

e088d65 Separate script/sign (jtimon)
9294a4b Separate CScriptCompressor (jtimon)
c4408a6 Separate script/standard (jtimon)
da03e6e Separate script/interpreter (jtimon)
cbd22a5 Move CScript class and dependencies to script/script (jtimon)
86dbeea Rename script.h/.cpp to scriptutils.h/.cpp (plus remove duplicated includes) (jtimon)

Rebased-by: Pieter Wuille
Merge pull request #4873

89d91f6 Avoid repeated lookups in mapOrphanTransactions and mapOrphanTransactionsByPrev (Wladimir J. van der Laan)
Remove some unnecessary c_strs() in logging and the GUI

Includes `core: remove unneeded c_str() / Qt: replace c_str() with Qt code`
by P. Kaufmann.