Various fixes and improvements of the new blame view

[tig] / TODO

TODO
----
Features that should be explored.

 - Better text-input support. From setsyx(3):

	The setsyx routine sets the virtual screen cursor to y, x. If y
	and x are both -1, then leaveok is set. The two routines getsyx
	and setsyx are designed to be used by a library routine, which
	manipulates curses windows but does not want to change the
	current position of the program cursor. The library routine
	would call getsyx at the beginning, do its manipulation of its
	own windows, do a wnoutrefresh on its windows, call setsyx, and
	then call doupdate.

 - When the user wants to "view" a commit, you could show from which
   branch heads and from which tags the commit is reachable, and perhaps
   which tag is the latest among the ones reachable from that commit, as
   part of the commit detail information you display on the lower pane
   (log/diff view).

 - Use non-blocking I/O + select() for incremental loading of view
   input. (debian bug #427093)

 - Split sources of tig.c into multiple files.

 - Rewrite revgraph handling.

 - Color the revgraph to make it easier to follow branches. Idea by
   Dominik Vogt