增加长期保存hls切片的功能，segKeep=0为不长期保存，segKeep=1为长期保存。此功能部分等效于segNum=0的情况，不同的是这个保留不会在m3u8文件中体现。

src/Record/HlsMakerImp.cpp

@@ -23,7 +23,8 @@ HlsMakerImp::HlsMakerImp(const string &m3u8_file,
                          const string &params,
                          uint32_t bufSize,
                          float seg_duration,
-                         uint32_t seg_number) : HlsMaker(seg_duration, seg_number) {
+                         uint32_t seg_number,
+                         bool seg_keep):HlsMaker(seg_duration, seg_number, seg_keep) {
     _poller = EventPollerPool::Instance().getPoller();
     _path_prefix = m3u8_file.substr(0, m3u8_file.rfind('/'));
     _path_hls = m3u8_file;
@@ -47,7 +48,7 @@ void HlsMakerImp::clearCache() {
 void HlsMakerImp::clearCache(bool immediately, bool eof) {
     //录制完了
     flushLastSegment(eof);
-    if (!isLive()) {
+    if (!isLive()||isKeep()) {
         return;
     }