[support_mailcmd] incoming emails can contain '\r\n' or '\r' instead of '\n' for newlines which causes problems

support_mailcmd_support_fetch_message_alter() explodes message body using '\n' but messages can contain '\r\n' or '\r' instead for new lines. This can causes the regex match to look like 'variable\r' or make the function fail in identifying variables which can cause problems. Just need to replace '\r\n' and '\r' with '\n' before exploding.