Add export_tarball tool.
Add export_tarball tool.

It creates a .bz2 tarball with all the sources, but without
.svn directories, and has an option to remove files
which are not required for build, and take a lot of space.

Review URL: http://codereview.chromium.org/155863

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@21384 0039d316-1c4b-4281-b951-d872f2087c98

yitian134/chromium,ropik/chromium,yitian134/chromium,gavinp/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,adobe/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,yitian134/chromium,ropik/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,yitian134/chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,adobe/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,adobe/chromium