AJP13 protocol parser

Tobias Begalke 4990ad476f payload length check 7 lat temu
ajp13.go 4990ad476f payload length check 7 lat temu
ajp13_test.go c0560ceda7 init 7 lat temu
header.go c0560ceda7 init 7 lat temu
method.go c0560ceda7 init 7 lat temu