Existing code was long, unclear and twisty.
This also relaxes the rules a tiny bit: allows to have
whitespace before header name and colon and makes the
header value match to be case-insensitive.
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
2abc22e639