Don't truncate long symlink paths.

Patch from Richard Purdie. Tracked as Issue #72. Original patch header follows.

If a tarball contains a long symlink (over 100 chars) in a longpath (over 100
chars) then the resulting link or path can be truncated to 100 chars.

This is due to a bug where if both 'L' and 'K' entries are found in the tarball,
only the first one takes affect due to get_header_tar recursively calling itself.
To fix this, process longname and linkname at the end of the function rather
than the start after any subcalls have taken place.

Richard Purdie
22/12/2010

git-svn-id: http://opkg.googlecode.com/svn/trunk@594 e8e0d7a0-c8d9-11dd-a880-a1081c7ac358