add lz4 compression to pctrace

incl/iss/plugin/pctrace.h

@@ -44,7 +44,7 @@
 
 namespace iss {
 namespace plugin {
-
+class lz4compress_steambuf;
 class cov : public iss::vm_plugin {
     struct instr_delay {
         std::string instr_name;
@@ -88,10 +88,13 @@ public:
 private:
     iss::instrumentation_if *instr_if  {nullptr};
     std::ofstream output;
+#ifdef WITH_LZ4
+    std::unique_ptr<lz4compress_steambuf> strbuf;
+    std::ostream ostr;
+#endif
     std::string filename;
     std::vector<instr_desc> delays;
-    bool jumped, first;
-
+    bool jumped{false}, first{true};
 };
 }
 }