Actually free the memory libvgz allocated to work in.

No wonder gzip support leaked memory...

Orginally this memory came from the the thread workspace so deallocation
was automatic.  Not so when we switched to malloc...

bin/varnishd/cache_gzip.c

@@ -80,6 +80,7 @@ SVNID("$Id$")
 struct vgz {
 	unsigned		magic;
 #define VGZ_MAGIC		0x162df0cb
+	enum {VGZ_GZ,VGZ_UN}	dir;
 	struct sess		*sess;
 	const char		*id;
 	struct ws		*tmp;
@@ -162,6 +163,7 @@ VGZ_NewUngzip(struct sess *sp, const char *id)
 
 	CHECK_OBJ_NOTNULL(sp, SESS_MAGIC);
 	vg = vgz_alloc_vgz(sp, id);
+	vg->dir = VGZ_UN;
 	VSC_main->n_gunzip++;
 
 	/*
@@ -182,6 +184,7 @@ VGZ_NewGzip(struct sess *sp, const char *id)
 
 	CHECK_OBJ_NOTNULL(sp, SESS_MAGIC);
 	vg = vgz_alloc_vgz(sp, id);
+	vg->dir = VGZ_GZ;
 	VSC_main->n_gzip++;
 
 	/*
@@ -380,6 +383,10 @@ VGZ_Destroy(struct vgz **vgp)
 	    (intmax_t)vg->vz.stop_bit);
 	if (vg->tmp != NULL)
 		WS_Reset(vg->tmp, vg->tmp_snapshot);
+	if (vg->dir == VGZ_GZ)
+		AZ(deflateEnd(&vg->vz));
+	else
+		AZ(inflateEnd(&vg->vz));
 	FREE_OBJ(vg);
 }