View source for Problem need to be settled in 4.3

Here we list some problem which can not be done for Fcitx 4.2, due to binary compatible and API compatible.

Rule: Something looks like reinvent the wheel, but actually it's avoid external breakage.

* Main loop module should not use fd_set, in order to make it be able to change the underlying system to epoll or any other things.
* FcitxHotkey should not be a array of 2, with ability to make it have more than one hotkey
* Deprecated GetOutString, Use FcitxInstanceCommitString instead.
* Deprecated GetRawInputString, maybe this should belong to input method.
* Merge FcitxInstance and FcitxInputState.
* Maybe we need a event based system to merge both "hook", "context", "timeout".
** DBus Maybe need to have ability to extend event system?
* Move FcitxConfigFile away from file system related interface.
** Certainly we will never go with gconf/dconf, they are so messy and fcitx will never use glib.
* Better test driven develop. Target is we can test everything that being added.