Fix CALC_SIZE: packages with a `+' in them messed it up.
Add a new option: ALT_FMT. This is an alternative format for
displaying packages to be installed, similar to other package
managers (like VoidLinux' xbps-install, for example).
Like CALC_SIZE, ALT_FMT is disabled by default.
Converted -u, -U and -X to using proc_pkgs.