gzip: flush output buffer after stored blocks only if necessary

function                                             old     new   delta
flush_block                                          671     680      +9

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/gzip.c b/archival/gzip.c
index 7df38c2..92130e7 100644
--- a/archival/gzip.c
+++ b/archival/gzip.c
@@ -634,7 +634,8 @@
 		put_8bit(*buf++);
 	}
 	/* The above can 32-bit misalign outbuf */
-	flush_outbuf_if_32bit_optimized();
+	if (G1.outcnt & 3) /* syscalls are expensive, is it really misaligned? */
+		flush_outbuf_if_32bit_optimized();
 }