List files with specified suffix

%GETFILELIST generates a list of files with specified suffix under topDir.

%GETFILELIST generates a list of files with specified suffix under topDir.
% This function lists files with specified suffix under topDir. It
% searches all levels of subfolders.
%
% FileList: a cell to store the list.
% topDir: top directory in which files are searched.
% suffix: type of files to search, default by AVI.
% outputFlag: a bool value to determine whether an output file is
% generated.
%
% Shiquan Wang @ CASIA
% [e-mail]/[e-mail]
% http://www.cbsr.ia.ac.cn/users/sqwang/
% revised on 2009/10/26