add an explicit close function to sndfile

NB. if someday we want to switch back to upstream
SndfileHandle, we need to subclass wrap it.
(not sure what else is different, anyway)

libs/audiographer/private/sndfile.hh

@@ -87,6 +87,8 @@ class SndfileHandle
 			SndfileHandle (const SndfileHandle &orig) ;
 			SndfileHandle & operator = (const SndfileHandle &rhs) ;
 
+			void close (void) ;
+
 		/* Mainly for debugging/testing. */
 		int refCount (void) const { return (p == NULL) ? 0 : p->ref ; }
 
@@ -152,6 +154,18 @@ inline
 SndfileHandle::SNDFILE_ref::~SNDFILE_ref (void)
 {	if (sf != NULL) { sf_close (sf) ; } }
 
+
+void
+SndfileHandle::close (void)
+{
+	if (p != NULL && --p->ref == 0)
+	{
+		delete p ;
+		p = NULL;
+	}
+}
+
+
 inline
 SndfileHandle::SndfileHandle (const char *path, int mode, int fmt, int chans, int srate)
 : p (NULL)