add http_client library, using libcurl

take out common http entities to http_common dir

libs/http_client/curl_thread_pool_p.h

@@ -0,0 +1,32 @@
+#ifndef curl_thread_pool_p_H
+#define curl_thread_pool_p_H
+
+#include "piconditionvar.h"
+#include "piprotectedvariable.h"
+#include "pisemaphore.h"
+#include "pithread.h"
+
+class PIHTTPClient;
+
+class CurlThreadPool {
+public:
+	void registerClient(PIHTTPClient * c);
+
+	static CurlThreadPool * instance();
+
+private:
+	NO_COPY_CLASS(CurlThreadPool)
+	CurlThreadPool();
+	~CurlThreadPool();
+
+	void threadFunc();
+	void procClient(PIHTTPClient * c);
+
+	PIProtectedVariable<PIQueue<PIHTTPClient *>> clients;
+	PISemaphore sem;
+	PIVector<PIThread *> threads;
+	std::atomic_bool exiting = {false};
+};
+
+
+#endif