In TStreamerBase::InitStreaming don't search on checksum when we can't.

This is one of two fixes for ROOT-6765 (and possibly ROOT-6779)
In TFile::ReadStreamerInfo properly handle the case of large files

This is the second of two fixes for ROOT-6765 (and possibly ROOT-6779)
TNetXNGFile: Make sure to handle echoed responses to readv_ior_max and readv_iov_max
Protection added against gPad==0 in order to fix https://sft.its.cern.ch/jira/browse/ROOT-6777.
The copy constructor was incomplete for some TLegend attributes.
It fixes https://sft.its.cern.ch/jira/browse/ROOT-6793
Allow to get a TClass instance via typedef name w/o parsing

performing the following steps:
0) Autoload based using the name of the typedef as key (was there already)
1) Check if the name is a typedef
2) If yes, try to get in the class table the TClass linked to the underlying
type. Do not use a nested GetClass call.
TNetXNGFile: when readv_iov_max is wrong assume that readv_ior_max is wrong too
Revert "Make NetXNG.QueryReadVParams settable by $ROOT_XRD_QUERY_READV_PARAMS."

This reverts commit 9e8ffe2f428adc2f77ceb24cca224b63e88a5dd8.
TXNetNG now detects bogus dCache settings automatically.
This ends ROOT-6639.
New example showing how to remove and add a stat line in a stat box.
Require complete type when checking for the base class (Solves ROOT-6750)

Also reduce code duplication relate to require complete types.
Speed up TFunction::TFunction
TMethodCall owns its TFunction, so always copy it (fixes ROOT-6435)
Disable DESTDIR when moving the headers in the build area (fixes ROOT-6803)
Doc improvements
Apply fixes suggested here: http://root.cern.ch/phpBB3/viewtopic.php?f=10&t=18743
Update the "Special return code" list
Avoid parsing if possible even if the user allows for it
Remove shadowing of parameter
Perf optimisation: check for tmplt args to suppress only if needed.
KeepNParams is now operational on stl containers: revert commit
Revert "Perf optimisation: check for tmplt args to suppress only if needed."

This reverts commit 67fab50f8b50838221bc2b8ca25ede6abfa7d5bf.