bunzip2/gunzip/uncompress/unlzma: merge into common code -

fix few corner cases, reduce size by 450 bytes. Update testsuite.

archival/rpm2cpio.c

@@ -79,7 +79,7 @@ int rpm2cpio_main(int argc, char **argv)
 		bb_error_msg_and_die("invalid gzip magic");
 	}
 
-	check_header_gzip(rpm_fd);
+	check_header_gzip_or_die(rpm_fd);
 	if (inflate_gunzip(rpm_fd, STDOUT_FILENO) < 0) {
 		bb_error_msg("error inflating");
 	}