Avoid an image being read as a base64-encoded text when it is posted via e-mail and its content-type is image/* (fixes #2261)
Avoid an image being read as a base64-encoded text when it is posted via e-mail and its content-type is image/* (fixes #2261)

nise-nabe/ppcon-sns,C-nakajima/OpenPNE3,isaosano/OpenPNE3,upsilon/travis-test,isaosano/OpenPNE3,kashiwasan/symfony-advanced,C-nakajima/OpenPNE3,isaosano/OpenPNE3,openpne/OpenPNE3,tejima/OP3PKG,C-nakajima/OpenPNE3,kashiwasan/symfony-advanced,ShinichiU/OpenPNE3,openpne/OpenPNE3,ShinichiU/AuthFramework,ShinichiU/OpenPNE3,ShinichiU/OpenPNE3,tejima/OP3PKG,C-nakajima/OpenPNE3,openpne/OpenPNE3,nishizoe/OpenPNE3,upsilon/travis-test,openpne/OpenPNE3,isaosano/OpenPNE3,ShinichiU/AuthFramework,ShinichiU/AuthFramework,nise-nabe/ppcon-sns,ShinichiU/OpenPNE3,nishizoe/OpenPNE3