[Qt] Change Coin control labels and tooltips because of non-rounding fees
Allocate receive buffers in on the fly
Fix formatting
Add CMutableTransaction and make CTransaction immutable.

In addition, introduce a cached hash inside CTransaction, to prevent
recalculating it over and over again.
Code simplifications after CTransaction::GetHash() caching
remove unused CNode::Cleanup()
add missing vhListenSocket.clear(); to CNetCleanup()
Merge pull request #4381

806fd19 Allocate receive buffers in on the fly (Pieter Wuille)
Merge pull request #4309

d38da59 Code simplifications after CTransaction::GetHash() caching (Pieter Wuille)
4949004 Add CMutableTransaction and make CTransaction immutable. (Pieter Wuille)
remove unneded class CNodeCombinedStats; from rpcconsole.cpp

- also 2 small style fixes
Merge pull request #4391

b612bde remove unneded class CNodeCombinedStats; from rpcconsole.cpp (Philip Kaufmann)
Merge pull request #4385

040c2d3 Fix formatting (Drak)
Merge pull request #4388

3dc1464 add missing vhListenSocket.clear(); to CNetCleanup() (Philip Kaufmann)
2831a03 remove unused CNode::Cleanup() (Philip Kaufmann)
Avoid undefined behavior using CFlatData in CScript serialization

`&vch[vch.size()]` and even `&vch[0]` on vectors can cause assertion
errors with VC in debug mode. This is the problem mentioned in #4239.
The deeper problem with this is that we rely on undefined behavior.

- Add `begin_ptr` and `end_ptr` functions that get the beginning and end
  pointer of vector in a reliable way that copes with empty vectors and
  doesn't reference outside the vector
(see https://stackoverflow.com/questions/1339470/how-to-get-the-address-of-the-stdvector-buffer-start-most-elegantly/1339767#1339767).
- Add a convenience constructor to CFlatData that wraps a vector.

I added `begin_ptr` and `end_ptr` as separate functions as I imagine
they will be useful in more places.
Merge pull request #4293

fa126ef Avoid undefined behavior using CFlatData in CScript serialization (Wladimir J. van der Laan)
doc: Remove unused section from release-process.md

It is outdated information. If we ever resurrect gitian-downloader it
can be brought back from history and updated.
Merge pull request #4314

b3c912d [Qt] Change Coin control labels and tooltips because of non-rounding fees (Cozz Lovan)
rework closesocket()

- make closesocket() the pure Win32 API call on Win32
- make closesocket() emulate the Win32 behaviour on all other OSes
extend and cleanup use of closesocket()

- add missing closesocket() calls for BindListenPort()
- always call closesocket() before printing any text (ensure consistent
  usage in the code)

changes in ConnectSocketDirectly() unrelated to closesocket():
- replace 3 following calls to WSAGetLastError() by storing result into
  nErr and use this in an if-clause
- convert an if() to an else if(), which removes an unneded check if the
  first case is true
add CSocket (RAII class that provides access to a SOCKET)