init the pkgTagFile with the size of the Release file

Release files are basically one big Section, so we might safe some
Resize circles by starting with the filesize.

Git-Dch: Ignore

apt-pkg/deb/deblistparser.cc

@@ -805,7 +805,7 @@ bool debListParser::LoadReleaseInfo(pkgCache::PkgFileIterator &FileI,
    map_ptrloc const storage = WriteUniqString(component);
    FileI->Component = storage;
 
-   pkgTagFile TagFile(&File);
+   pkgTagFile TagFile(&File, File.Size());
    pkgTagSection Section;
    if (_error->PendingError() == true || TagFile.Step(Section) == false)
       return false;

apt-pkg/indexrecords.cc

@@ -62,7 +62,7 @@ bool indexRecords::Load(const string Filename)				/*{{{*/
    if (OpenMaybeClearSignedFile(Filename, Fd) == false)
       return false;
 
-   pkgTagFile TagFile(&Fd);
+   pkgTagFile TagFile(&Fd, Fd.Size());
    if (_error->PendingError() == true)
    {
       strprintf(ErrorText, _("Unable to parse Release file %s"),Filename.c_str());