terminal: Update terminal->end whenever we write a character
terminal: Update terminal->end whenever we write a character

We used to only update it on newline, which breaks when somebody moves
the cursor below terminal->end and writes stuff.  Instead update it whenever
we write a character to the terminal.

https://bugs.freedesktop.org/show_bug.cgi?id=71935

xorgy/weston,udoprog/weston,kwm81/weston,kwm81/weston,giucam/weston,eyolfson/weston,krezovic/weston,eyolfson/weston,mchalupa/weston,giucam/weston,Tarnyko/weston-xdg_surface_present,sir-murray/weston,sir-murray/weston,krezovic/weston,Tarnyko/weston-xdg_surface_present,udoprog/weston,xorgy/weston,Fantu/compositor-spice,Gnurou/weston,jonnylamb/weston,Gnurou/weston,mchalupa/weston,Fantu/compositor-spice,jonnylamb/weston,Fantu/compositor-spice