Fixed the bug that web-seed URI is not percent-encoded.
* src/a2functional.h
* src/bittorrent_helper.cc
* test/BittorrentHelperTest.cc
* test/url-list-multiFile.torrent
* test/url-list-singleFileEndsWithSlash.torrent
Added the ability to recognize url-list in a torrent file.
The retrieved URLs are attached to the corresponding FileEntry.
* src/DefaultBtContext.{h, cc}
* src/FileEntry.{h, cc}
* test/DefaultBtContextTest.cc