Don't make backup of znc.conf readable by everyone.

It doesn't really matter, since the whole ~/.znc/ is not readable, but
it's better to be safe.

src/FileUtils.cpp

@@ -249,6 +249,10 @@ bool CFile::Copy(const CString& sOldFileName, const CString& sNewFileName, bool
 	OldFile.Close();
 	NewFile.Close();
 
+	struct stat st;
+	GetInfo(sOldFileName, st);
+	Chmod(sNewFileName, st.st_mode);
+
 	return true;
 }