update symbol file (thanks to david)

debian/apt.symbols

@@ -1318,3 +1318,6 @@ libapt-pkg.so.4.10 libapt-pkg4.10
  (c++|optional=private)"debListParser::NewProvidesAllArch(pkgCache::VerIterator&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)@Base" 0.8.13.2 1
  (c++|optional=private)"PrintMode(char)@Base" 0.8.13.2 1
  (c++)"pkgDepCache::IsModeChangeOk(pkgDepCache::ModeList, pkgCache::PkgIterator const&, unsigned long, bool)@Base" 0.8.13.2 1
+ (c++)"pkgPackageManager::SmartUnPack(pkgCache::PkgIterator, bool)@Base" 0.8.15~exp1 1
+ (c++)"pkgAcqMethod::PrintStatus(char const*, char const*, char*&) const@Base" 0.8.15~exp1 1
+ (c++)"pkgCache::DepIterator::IsNegative() const@Base" 0.8.15~exp1 1