Rename gnome-terminal, vimrc-after.

Mod:
	gnome-terminal > gnome_terminal, vimrc-after > vimrc_after
		-rename by replacing dashes with underscores, in keeping with my
		(now revised) filename conventions.

	vim/ftplugin/*.vim
		-change "so ~/.vimrc-after" to "so ~/.vimrc_after" accordingly.