i18n: fix "% inside _()" problems Before this patch, "contrib/check-code.py" can't detect these problems, because the regexp pattern to detect "% inside _()" doesn't suppose the case that format string consists of multiple string components concatenated implicitly or explicitly, This patch does below for that regexp pattern to detect "% inside _()" problems in such case. - put "+" into separator part ("[ \t\n]") for explicit concatenation ("...." + "...." style) - enclose "component and separator" part by "(?:....)+" for concatenation itself ("...." "...." or "...." + "....")