reduce duplicate calling (syscall-fcntl, strstr)
allocate file buffer if need, to reduce calling malloc
allocate FILE structs in advance, and reuse them after calling fclose.

Issue: #I7CF8X
Test:libc-test, benchmark, wukong test
Signed-off-by: NWang Yaofeng <wangyaofeng.wang@huawei.com>
Change-Id: I12585e1ad99b8dbecbbaec1d259d26c58f266cd0