imbue .diff/Index parsing with C.UTF-8 as well

In 3bdff17c894d0c3d0f813d358fc45d7a263f3552 we did it for the datetime
parsing, but we use the same style in the parsing for pdiff (where the
size of the file is in the middle of the three fields) so imbueing here
as well is a good idea.

apt-pkg/acquire-item.cc

@@ -2000,6 +2000,7 @@ bool pkgAcqDiffIndex::ParseDiffIndex(string const &IndexDiffFile)	/*{{{*/
    HashStringList ServerHashes;
    unsigned long long ServerSize = 0;
 
+   auto const &posix = std::locale("C.UTF-8");
    for (char const * const * type = HashString::SupportedHashes(); *type != NULL; ++type)
    {
       std::string tagname = *type;
@@ -2011,6 +2012,7 @@ bool pkgAcqDiffIndex::ParseDiffIndex(string const &IndexDiffFile)	/*{{{*/
       string hash;
       unsigned long long size;
       std::stringstream ss(tmp);
+      ss.imbue(posix);
       ss >> hash >> size;
       if (unlikely(hash.empty() == true))
 	 continue;
@@ -2089,6 +2091,7 @@ bool pkgAcqDiffIndex::ParseDiffIndex(string const &IndexDiffFile)	/*{{{*/
       string hash, filename;
       unsigned long long size;
       std::stringstream ss(tmp);
+      ss.imbue(posix);
 
       while (ss >> hash >> size >> filename)
       {
@@ -2147,6 +2150,7 @@ bool pkgAcqDiffIndex::ParseDiffIndex(string const &IndexDiffFile)	/*{{{*/
       string hash, filename;
       unsigned long long size;
       std::stringstream ss(tmp);
+      ss.imbue(posix);
 
       while (ss >> hash >> size >> filename)
       {
@@ -2184,6 +2188,7 @@ bool pkgAcqDiffIndex::ParseDiffIndex(string const &IndexDiffFile)	/*{{{*/
       string hash, filename;
       unsigned long long size;
       std::stringstream ss(tmp);
+      ss.imbue(posix);
 
       // FIXME: all of pdiff supports only .gz compressed patches
       while (ss >> hash >> size >> filename)