Split out UI functions for todo items

* Move todo-related UI functions from "interaction.c" to a new
  compilation unit "ui-todo.c".

* Rename all todo-related UI functions to todo_ui_*().

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/Makefile.am

@@ -32,6 +32,7 @@ calcurse_SOURCES = \
 	sha1.c \
 	sigs.c \
 	todo.c \
+	ui-todo.c \
 	utf8.c \
 	utils.c \
 	vars.c \