ValidateRequestHeaders now not only accept ", " as separator
ValidateRequestHeaders now not only accept ", " as separator

see RFC2616:
message-header = field-name ":" [ field-value ]
       field-name     = token
       field-value    = *( field-content | LWS )

CR             = <US-ASCII CR, carriage return (13)>
LF             = <US-ASCII LF, linefeed (10)>
SP             = <US-ASCII SP, space (32)>
HT             = <US-ASCII HT, horizontal-tab (9)>
CRLF           = CR LF
LWS            = [CRLF] 1*( SP | HT )

itsjamie/gin-cors