Enable backtrace stuff only if GNU C library used, because current
backtrace implementation based on <execinfo.h> , which is not a
part of standard C library, it is a GNU extension.
This will be usefull when building with custom POSIX-compilant C
library (like musl) and no <execinfo.h> available.
Note: configure script will detect presence of <execinfo.h> and
enable/disable feature depending on it.
Feature is enabled by default.
It may be useful to have different configurations either for portable
versions or for debugging purposes. To implement this we add two
options, avaliable via command line switches
1. An option to change configuration name ("--configuration"). The name
supplied via this option is appended to
QCoreApplication::applicationName() to form "qBittorrent_<conf_name>"
name for the configuration files.
2. An option to provide a path do directory where all the settings are
stored (kind of profile directory). There is a shortcut "--portable"
which means "use directory 'profile' near the executable location".
In order to implement that we have to perform initialisation of the
profile directories before the SettingStorage and Preferences singletones
are initialised. Thus, options parsing shall be performed without defaults
read from preferences.
Application process message and split it into params list itself (this
prevents code duplication).
Application store params unless other components ready to process them.
Application incapsulate all QMacApplication and SessionApplication logic
(this is too small to have separate classes).
Change project directory structure according to application structure.
Change 'nox' configuration option to something more meaningful 'nogui'.
Rename 'Icons' folder to 'icons' (similar to other folders).
Partially add 'nowebui' option support.
Remove QConf project file.
