progress bar support

based on:
http://nsis.sourceforge.net/Talk:UnTGZ_plug-in
http://pastebin.com/ZrSGG72D

but support for larger files

seems to support lzma only for now
improved progressbar support

start at 0 now.
gzip+bz2 extraction now also supported
larger file size now potentially supported (__int64) as long as the
underyling decompression code supports it

tested with 2.8 gb for now