Fixes error
Only remove actualy failed blocks from setBlockIndexValid
Only keep setBlockIndexValid entries that are possible improvements
Reject transactions with excessive numbers of sigops
Add helptexts for -whitelist and rpc prioritisetransaction and switch to bitcoin instead of satoshis
Add a new checkpoint at block 295,000

Block 295,000 seems to meet the criteria of a reasonable timestamp and
no strange transactions. 295,000 is the current block height in the
bootstrap.dat torrent provided by jgarzik.
net: add SetSocketNonBlocking() as OS independent wrapper
additional test for OP_SIZE in script_valid.json
script tests: BOOLAND, BOOLOR decode to integer

unlike other boolean checks, arguments >5 bytes invalidate the script
script tests: values that overflow to 0 are true
script tests: value with trailing 0x00 is true
script test: test case for 5-byte bools
Introduce option to disable relay/mining of bare multisig scripts in TX outputs

First and foremost, this defaults to OFF.

This option lets a node consider such transactions non-standard,
meaning they will not be relayed or mined by default, but other miners
are free to mine these as usual.
script tests: add tests for CHECKMULTISIG limits
Update README.md

Added two modifications to make the descriptions more clear.
qt: Make error message for failed export a little friendlier

Closes #4528.
Merge pull request #3939

3da434a Introduce option to disable relay/mining of bare multisig scripts in TX outputs (Jeff Garzik)
[Qt] Fix thin space in URI
Merge pull request #4563

027dcdc [Qt] Fix thin space in URI (Cozz Lovan)
qt: Move SplashFinished to after ClientModel/WalletModel creation

With a large wallet there was a noticable gap between hiding of the
splash and showing the main window.