Use seek/tell instead of offset line by line

This patch refactor the code to use seek/tell perl functions instead of
looking for the correct offset line by line. This makes logsaw much more
faster than previously (dramaticaly with flat file!).
Moreover, replace "IO::Zlib" with IO::Uncompress::AnyUncompress, which
is faster, support seek, and support more compression format.
Apply perltidy on logsaw

This is the pertidy command used:

  perltidy -nola logsaw