Change GLib size units policy

Change GLib size units policy

This commit changes GLib size units policy.  We now prefer SI units and
allow for use of proper IEC units where desired.

g_format_size_for_display() which incorrectly mixed IEC units with SI
suffixes is left unmodified, but has been deprecated.

g_format_size() has been introduced which uses SI units and suffixes.

g_format_size_full() has also been added which takes a flags argument to
allow for use of IEC units (with correct suffixes).  It also allows for
a "long format" output which includes the total number of bytes.  For
example: "238.5 MB (238,472,938 bytes)".