[Qt] fix RecentRequestsTableModel function ambiuguity

- fixes a compiler ambiguity error with ::createIndex() called in
  RecentRequestsTableModel::index()
- also add some Q_UNUSED() macros
Squashed 'src/leveldb/' changes from 936b461..e991315

e991315 Merge upstream LevelDB 1.15.
0cfb990 Release LevelDB 1.15
02ac9f1 Merge upstream LevelDB 1.14.
0b9a89f Release LevelDB 1.14

git-subtree-dir: src/leveldb
git-subtree-split: e991315d7fe4ca84a98902578106cbffa3dcccfd
Merge src/leveldb changes for LevelDB 1.15
Rebrand to `Bitcoin Core`

Only messages for now, executable names and other file names
can be changed later if necessary and safe.

Do not do an all-sweeping change. Some occurences of Bitcoin-Qt need to
be kept:

- Applicationname: this is used to determine the registry entry names,
  we don't want to lose settings over a silly name change.
- Where it refers to the executable name instead of the product name.
Remove unused ThreadSafeHandleURI from ui_interface
Remove unused ThreadSafeAskFee from ui_interface

ThreadSafeAskFee is effectively unused. It is only called
when the fAskFee parameter on SendMoney or SendMoneyToDestination
is true, which never happens. Remove it.
Improve unit test code not to compare with explanatory messages for each platform.
Instead, use have an exception object to check if the string returned by what() on the raised exception matches the string returned by what() on the expected exception instance.
This way, we do not need to list all different possible explanatory strings for different platforms in the test code, and make it simple. (The idea is by Cory Fields.)
Merge pull request #3423

0205abd Improve unit test code not to compare with explanatory messages for each platform. Instead, use have an exception object to check if the string returned by what() on the raised exception matches the string returned by what() on the expected exception instance. This way, we do not need to list all different possible explanatory strings for different platforms in the test code, and make it simple. (The idea is by Cory Fields.) (Kangmo)
qt: status WalletModel::Aborted is no longer used

Aborting transactions happens in the GUI now as it should,
not the backend.
Seperate out wallet options in help message

Seperate out the wallet options in HelpMessage, and
don't show them if compiled with --disable-wallet.

Also add documentation for `-disablewallet` option.
Merge pull request #3408

22f0135 Rebrand to `Bitcoin Core` (Wladimir J. van der Laan)
qt: Update English language file for translators
Merge pull request #3425

88ba264 qt: Update English language file for translators (Wladimir J. van der Laan)
Fix typo in unit-tests.md
Merge pull request #3430 from ldenman/patch-1

Fix typo in unit-tests.md
Fix typos in spendfrom README
some more small re-branding changes (Bitcoin Core)
Merge pull request #3434

46469d0 some more small re-branding changes (Bitcoin Core) (Philip Kaufmann)
Merge pull request #3431

131c3db Fix typos in spendfrom README (Lake Denman)
[Qt] style-police, add missing license headers

- add missing license headers in Mac files
- small code formating cleanups