2008-05-13 Tatsuhiro Tsujikawa <tujikawa at rednoah dot com>

Replaced "" with static const variable A2STR::NIL.
	Replaced string comparison against "" with std::string::empty().
	Added PROTO_* to Request class and use them as a protocol string
	constant.
	Made "started", "stopped", "completed" static const variable in
	AnnounceList class.

src/HttpHeaderProcessor.cc

@@ -38,6 +38,7 @@
 #include "Util.h"
 #include "DlRetryEx.h"
 #include "DlAbortEx.h"
+#include "A2STR.h"
 
 namespace aria2 {
 
@@ -90,7 +91,7 @@ size_t HttpHeaderProcessor::getPutBackDataLength() const
 
 void HttpHeaderProcessor::clear()
 {
-  strm.str("");
+  strm.str(A2STR::NIL);
 }
 
 SharedHandle<HttpHeader> HttpHeaderProcessor::getHttpResponseHeader()