check-code: detect "% inside _()" when there are leading whitespaces
Before this patch, "contrib/check-code.py" can't detect "% inside _()"
correctly, when there are leading whitespaces before the format
string, like below:
_(
"format string %s" % v)
This patch adds regexp pattern "[ \t\n]*" before the pattern matching
against the format string.
"[\s\n]" can't be used in this purpose, because "\s" is automatically
replaced with "[ \t]" by "_preparepats()" and "\s" in "[]" causes
nested "[]" unexpectedly.