Fix issue with the import message commands introduced in previous commit

The fread() usage here did not need "addressing" (Commit 27fb52a1).

This caused messages posted via smbutil to be short (e.g. 0 or 1 bytes
in length). Reported by Accession via Idle Relay Chat.

Also, don't call strlen() on msgtxt which could be NULL, causing segfault
in final printf() callin in postmsg().

src/sbbs3/smbutil.c

@@ -207,7 +207,7 @@ void postmsg(char type, char* to, char* to_number, char* to_address,
 	/* Read message text from stream (file or stdin) */
 	msgtxtlen=0;
 	while(!feof(fp)) {
-		i=fread(buf,sizeof(buf),1,fp);
+		i=fread(buf,1,sizeof(buf),fp);
 		if(i<1)
 			break;
 		if((msgtxt = realloc(msgtxt,msgtxtlen+i+1))==NULL) {
@@ -369,7 +369,7 @@ void postmsg(char type, char* to, char* to_number, char* to_address,
 	smb_freemsgmem(&msg);
 
 	// MSVC can't do %zu for size_t until MSVC 2017 it seems...
-	fprintf(statfp, "Message (%" PRIu64 " bytes) added to %s successfully\n", (uint64_t)strlen((char *)msgtxt), smb.file);
+	fprintf(statfp, "Message (%ld bytes) added to %s successfully\n", msgtxtlen, smb.file);
 	FREE_AND_NULL(msgtxt);
 }