Fix for missing libraries (OSX Big Sur) (alisw#20)

Co-authored-by: hristov <[email protected]>

Make GetEntriesSerialized actually work with destructive serialization

TBulkRead::GetEntriesSerialized should simply work with destructive
serialization. Not sure why the check is there.

TBranch::GetBulkEntries proper handling of already loaded basket

This fixes Issue root-project#6416 and Issue root-project#6417

Tag patch release v6.20/08.

Fix build with external libpng

Invert opt noGlobalUsingStd(def=false) to globalUsingStd(def=false)

With this patch the rootcling option noGlobalUsingStd (by default off) preventing declaration of
{using namespace std} in the global scope is inverted to option globalUsingStd(def=false) which allow
to declare using std. Therefore, by default the pollution of the global scope will be forbidden but
optionally can be requested.

Avoid {using namespace std} in global scope of dictionary [ROOT-10661]

In order to avoid {namespace std} interfering with following include files,
when generating a dictionary file add the {using namespace std;} only after
GenerateNecessaryIncludes method is called.

Since many legacy root header files do require this global {using namespace std;}
to complete the tests, old behaviour is kept by default and the global
{using namespace std} can be avoided by adding -noGlobalUsingStd to rootcling invocation.

Allow passing ACLiC RootCling flags via .rootrc (Vassil)

This is a special patch tailored for v6-20-02

Fix tests arrow tests

Workaround detection of non-official tags

Read size of archive member when accessing directly