This adds a second parameter to size_to_human_string() to return a

This adds a second parameter to size_to_human_string() to return a
string with a different format based on the following flags:

        SIZE_SUFFIX_1LETTER  = "1K"
        SIZE_SUFFIX_3LETTER  = "1KiB",
        SIZE_SUFFIX_SPACE    = "1 KiB" or "1 K"

[kzak@redhat.com: - rename flags to SIZE_SUFFIX_* format,
                  - fix suffix[] buffer size
                  - add 3 letter version to the test]

Signed-off-by: Francesco Cosoleto <cosoleto@gmail.com>
Signed-off-by: Karel Zak <kzak@redhat.com>