Fix build with for -Werror=format-truncation

Growing log size string to meet maximal username/hostname string sizes

--- src/ftp.h

+++ src/ftp.h

@@ -176,7 +176,7 @@ typedef struct _ftp {

     int			ccpcoll;

     FILE		*xlfp;

-    char		logusername[100];

+    char		logusername[300];

     int			commands;

     unsigned long datain, dataout;