Move seamless .Z support into unpack_gz_stream

unpack_gz_stream                                     566     643     +77
unpack_gunzip                                        123      12    -111

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/Config.src b/archival/Config.src
index 885cb5b..ae1afc5 100644
--- a/archival/Config.src
+++ b/archival/Config.src
@@ -32,10 +32,10 @@
 	  Make tar, rpm, modprobe etc understand .gz data.
 
 config FEATURE_SEAMLESS_Z
-	bool "Make tar and gunzip understand .Z data"
+	bool "tar, rpm, modprobe etc understand .Z data"
 	default n
 	help
-	  Make tar and gunzip understand .Z data.
+	  Make tar, rpm, modprobe etc understand .Z data.
 
 config AR
 	bool "ar"