fetch: align per-ref summary report in UTF-8 locales

fetch: align per-ref summary report in UTF-8 locales

fetch does printf("%-*s", width, "foo") where "foo" can be a utf-8
string, but width is in bytes, not columns. For ASCII it's fine as one
byte takes one column. For utf-8, this may result in misaligned ref
summary table.

Introduce gettext_width() function that returns the string length in
columns (currently only supports utf-8 locales). Make the code use
TRANSPORT_SUMMARY(x) where the length is compensated properly in
non-English locales.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>