Refine compression of Windows installer

I increased the efficiency of LZM compression of makecab. I found that we can use .Set CompressionMemory=21 setting. This setting produces 83,91% of original installer size and if we combine it with a simple zip compression the download size can reduce to 83,54%.

Reference:
http://www.mail-archive.com/libreoffice@lists.freedesktop.org/msg07068.html

setup_native/source/win32/nsis/downloadtemplate.nsi

@@ -3,8 +3,9 @@
 !define PRODUCT_PUBLISHER "PUBLISHERPLACEHOLDER"
 !define PRODUCT_WEB_SITE "WEBSITEPLACEHOLDER"
 
-SetCompressor lzma
-; SetCompressor zlib
+SetCompressor zlib
+SetDatablockOptimize On
+
 ; Helpful for debugging, disable for products
 ; RequestExecutionLevel user