- it was possible to trigger an infinite loop in FreespaceChecker::check() by
simply removing the drive letter on Windows (which leads to an infinite
loop in the FreespaceChecker thread)
- this was caused by not checking if we make progress with
parentDir.parent_path()
This adds an introduction screen that is shown when the client is first
started in which the user can choose a data directory.
It is also possible to force the intro screen to appear using command
line argument `-choosedatadir`.
The user is warned that the client will download and store 10Gb of data.
The intro screen shows how much space is available on the device that
contains the chosen directory and warns if this is less than the 10Gb.
To make it possible to translate the introduction dialog, the initialization
sequence is changed so that translations are
loaded before the data directory. This has the by-effect that it is
no longer possible to specify a language in bitcoin.conf inside the data
directory.
