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;