* configure.in: check for GTK+ 2.2, and if found, force use of multihead-safe
	APIs to try to flush out some bugs.
* src/vte.c, src/vteapp.c, src/vtedraw.c, src/vtefc.c, src/vteglyph.c: clean
	up some sloppy multihead changes.
* src/vte.c, src/vte.h (vte_terminal_match_set_cursor_type): add.
* src/vtedraw.c, src/vtedraw.h: add a draw_char() method which is allowed to
	fail.
* src/vte.c(vte_terminal_draw_graphic): separate the width of a column and the
	number of columns to be drawn.  Use _vte_draw_char() to avoid
	crude approximations of characters when we have a font for them.