playlist/Plugin: pass InputStreamPtr&& to open_stream()

Obsolete class CloseSongEnumerator, which was a kludge.

src/input/TextInputStream.cxx

@@ -26,6 +26,11 @@
 
 #include <assert.h>
 
+TextInputStream::TextInputStream(InputStreamPtr &&_is)
+	:is(std::move(_is)) {}
+
+TextInputStream::~TextInputStream() {}
+
 char *
 TextInputStream::ReadLine()
 {
@@ -54,7 +59,7 @@ TextInputStream::ReadLine()
 		--dest.size;
 
 		Error error;
-		size_t nbytes = is.LockRead(dest.data, dest.size, error);
+		size_t nbytes = is->LockRead(dest.data, dest.size, error);
 		if (nbytes > 0)
 			buffer.Append(nbytes);
 		else if (error.IsDefined()) {

src/input/TextInputStream.hxx

@@ -20,12 +20,13 @@
 #ifndef MPD_TEXT_INPUT_STREAM_HXX
 #define MPD_TEXT_INPUT_STREAM_HXX
 
+#include "input/Ptr.hxx"
 #include "util/StaticFifoBuffer.hxx"
 
 class InputStream;
 
 class TextInputStream {
-	InputStream &is;
+	InputStreamPtr is;
 	StaticFifoBuffer<char, 4096> buffer;
 
 public:
@@ -35,12 +36,16 @@ public:
 	 *
 	 * @param _is an open #InputStream object
 	 */
-	explicit TextInputStream(InputStream &_is)
-		:is(_is) {}
+	explicit TextInputStream(InputStreamPtr &&_is);
+	~TextInputStream();
 
 	TextInputStream(const TextInputStream &) = delete;
 	TextInputStream& operator=(const TextInputStream &) = delete;
 
+	InputStreamPtr &&StealInputStream() {
+		return std::move(is);
+	}
+
 	/**
 	 * Reads the next line from the stream with newline character stripped.
 	 *