Streamline UI ↔ Core interface

[laanwj]

This is a grab-bag of commits designed to streamline the UI↔Core interface. It contains various small improvements as well as code cleanups:

Improvements:

• Allow other threads to queue shutdown in UI thread (functionality in case of bitcoind is unchanged). RPC stop and encryptwallet will now work with UI, and this also fixes segfault part of v0.6.0rc5 segfault on initial blockchain download when out of diskspace #999.
• update UI only when needed, instead of polling with a timer (core notifies UI using AddressBookRepaint / MainFrameRepaint functions)
  • This fixes the issue with address created using RPC 'getnewaddress' not appearing in UI address book
• use a messagebox to display the error when -server is provided without providing rpcpassword, this doesn't get lost like a message to the console (functionality in case of bitcoind is unchanged)
• allow threads to request a modal dialog box for fatal errors, so that they can wait with shutting down until the user clicked OK (disk space error, etc)

Code cleanups:

• move QT_PLUGINS stuff to qt main file, where it belongs
• move dummy translation function _ to qtui.h/noui.h instead of util.h
• remove dependency for SecureString on serialize.h and util.h (and the rest of the knot of .h files) by moving allocators to new include file allocators.h
• remove broken and/or unnecessary functions from qtui.h/noui.h, clarify names, and leave only one MessageBox function that can be used both from AppInit2 and other threads

In principle, these commits are fairly independent and could be separate pull requests if necessary.

[sipa]

It looks all sane and functional to me.

[laanwj]

I have to think about point 2 a bit more though: do changes in statistics like the # of connections or the number of blocks trigger a MainFrameRepaint? I don't think so, and doing that could potentially result in a deluge of cross-thread notifications.

It does make sense to poll those statistics with a timer, just not the well-delineated updates to the transaction list (and balance), address book.

[laanwj]

To answer my own question: yes, MainFrameRepaint is called when the number of connections changes / number of blocks count. This is safe.

[sipa]

ACK on the code changes to core, but needs rebasing.

[laanwj]

Ok, this is all rebased and ready now.

[Diapolo]

Small question in qtgui.h and nogui.h I saw "#define wxMessageBox MyMessageBox" , is there some old wx code in, that can be removed, too?

Edit: Ah you removed that already :), nice and ACK!

[laanwj]

Yep! the only wx* definitions left are the flags to signal the message kind. They can be renamed, and a lot of can go, too, but I haven't determined yet which ones are useful (also in the future) and what to rename them to. Let's leave that to a later decision.

Edit: and can also be deduplicated and defined in a common header; there is no need to define them differently in qtui/noui.h.
Edit.2: thinking about it, there is no need for separate qtui.h / noui.h headers at all if we don't define implementations in the headers, which would be a sane thing to do anyway. The distinction could be made by linking bitcoind against a different implementation file.

[Diapolo]

Sounds pretty good.

[laanwj]

I've added another code cleanup / deduplication commit: Move from noui.h / qtui.h to one ui_interface.h with dummy implementation for the daemon.