Minor changes to fix the CMake builds for latest Axel's push.
Delay evaluation of COREO; SYSTEMO gets added only later.
Avoid unnecessary round-trip through string based interface
Pass the file to BuildCheck rather than using gDirectory
Add support for kCharStar in CompareContent
Use CompareContent also in PostLoadCheck
Bundle the looping over the legacy checksum check.

Add TClass::MatchLegacyCheckSum and TStreamerInfo::MatchLegacyCheckSum
to factor the looping over the set of legacy version of the checksum
calculations.
Expand doc to add some more historical information.
Consistently use ECheckSum.

ELegacyCheckSum has been renamed ECheckSum and is now used as part
of the GetCheckSum interface.
Implement new CheckSum (without typedefs)

The new checksum use the normalize type where the typedef have been
removed except for the opaque one (Double32_t, Float16_t, string,
Long64_t, etc.)
Fix direction of error message
Add code for backward comp. for broken case of abstract classes.

The code would be necessary only in very rare case and is added
here (but hidden behind an ifdef) in case this becomes a blocker.
One of the case would an abstract class that was written to
ROOT file older than v5.18 and in a circurcunstance that led
to an empty TStreamerInfo to be stored in the file and
if in addition one of the data member was declared using a
typedef _and_ the current class definition uses a different typedef.
Fix CompareContent for collection with typedef.

When testing a collection and there is a name mismatch, check not only
the name but also the content (and fix the v5 name as necessary).

In addition the previous test/condition was looking at the wrong names.
Prefer newer StreamerInfo.

When the class is loaded or known to the interpreter and the TStreamerInfo being read from
a file is equivalent (different checksum but same real content), we need to prefer the
one from in-memory as it would have better names (for the classes).
ResolveTypedef should never resolves Double32_t
Better way of combining the various older checksum calculation
Correct test direction (in GetCheckSum)
 Also keep/re-add Long64_t in CheckSums
Add support to merge top level non-TObject
In FindStreamerInfo special case current checksum.

This allows for the creation of the current streamerInfo if requested