top: extend new 'X' command to include the TTY field

I have no idea what the maximum length of a terminal
name might be.  However, the library provides for up
to 128 characters (ouch).

So just to be safe, this commit extends the ability
to widen columns to embrace this field.

Signed-off-by: Jim Warner <james.warner@comcast.net>

top/top.1

@@ -978,6 +978,7 @@ This \*(CI can be used to alter the widths for the following fields:
     RUID      5       RUSER     8
     SUID      5       SUSER     8
     UID       5       USER      8
+                      TTY       8
 .Ed
 
 You will be prompted for the amount to be added to the default

top/top.c

@@ -1899,6 +1899,8 @@ static void zap_fieldstab (void) {
    Fieldstab[P_UEN].width = Fieldstab[P_URN].width
       = Fieldstab[P_USN].width = Fieldstab[P_GRP].width
       = Rc.fixed_widest ? 8 + Rc.fixed_widest : 8;
+   Fieldstab[P_TTY].width
+      = Rc.fixed_widest ? 8 + Rc.fixed_widest : 8;
 
    // lastly, ensure we've got proper column headers...
    calibrate_fields();