Only remove actualy failed blocks from setBlockIndexValid
Bugfix: make CCoinsViewMemPool support pruned entries in underlying cache
qt: Use fixed-point arithmetic in amount spinbox

Fixes various issues and cleans up code

- Fixes issue #4500: Amount widget +/- has floating point rounding artifacts
- Amount box can now be emptied again, without clearing to 0

Also aligns the amount to the right, as in other places.
qt: Remove unused functions from BitcoinUnits

Remove two functions that are now unused.
ui: Make sure sendcoinsentry signals only connected once

Move signal connections to constructor where possible.
Merge pull request #4556

29eaa31 ui: Make sure sendcoinsentry signals only connected once (Wladimir J. van der Laan)
2a05101 qt: Remove unused functions from BitcoinUnits (Wladimir J. van der Laan)
91cce17 qt: Use fixed-point arithmetic in amount spinbox (Wladimir J. van der Laan)
doc: remove any mention of SOCKS4

SOCKS4 support was removed in 0127a9b, as well as the `-socks=` option.
Fix typos in comments (missing i's).
Merge pull request #4575

ad08d0b Bugfix: make CCoinsViewMemPool support pruned entries in underlying cache (Pieter Wuille)
Merge pull request #4496

5734d4d Only remove actualy failed blocks from setBlockIndexValid (Pieter Wuille)
Add comment about never updating nTimeOffset past 199 samples

Refer to issue #4521 for details.