Move functions and variables from guifuncs.[ch] to dcf77pi.c.

guifuncs was formerly a sink to handle all common ncurses functionality
in versions 2.0.0 to 2.1.0 but all that has already been moved to dcf77pi

Update included headers.
Remove guifuncs.[ch] from Makefile and delete the files.
Remove empty 'hdrfile' definition