merge: fix swapped "up to date" message components

merge: fix swapped "up to date" message components

The rewrite of git-merge from shell to C in 1c7b76be7d (Build in merge,
2008-07-07) accidentally transformed the message:

    Already up-to-date. (nothing to squash)

to:

    (nothing to squash)Already up-to-date.

due to reversed printf() arguments. This problem has gone unnoticed
despite being touched over the years by 7f87aff22c (Teach/Fix pull/fetch
-q/-v options, 2008-11-15) and bacec47845 (i18n: git-merge basic
messages, 2011-02-22), and tangentially by bef4830e88 (i18n: merge: mark
messages for translation, 2016-06-17) and 7560f547e6 (treewide: correct
several "up-to-date" to "up to date", 2017-08-23).

Fix it by restoring the message to its intended order. While at it, help
translators out by avoiding "sentence Lego".

[es: rewrote commit message]

Co-authored-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>