Fix for ROOT-5923

Fully treat the 'xroot' protocol as the 'root*' in FindHelper. Remove warning due to a first
call of the related plugin with a wrong number of arguments.
Renamed option c++11 to cxx11 (the one used for ROOT6) and try to keep some compatibility. Fixes ROOT-6169
Add Anna
fix https://sft.its.cern.ch/jira/browse/ROOT-6209
put entries in alphabetic order.
update comments on opaque options.
New font metrics in TVirtualX.
The new code for CTLine (metrics).
Update FontCache to calculate new metrics.
New font metrics in TGQuartz.
Text "extent" and mods in TText to use new metrics (if implemented)

for non-TTF back-ends.
Line width 0 is also possible.
When the text size is too small the line width for the square root and the bars must be 1 pixel.
Fix typo
Implement \splitline for TeX output.
allow import and auto-loading to play together
Remove const warning in operator<< for TArray*
Fix TH1::Merge for merging histograms with buffer with histogram with limits
Add tests for merging histogram with buffer in stressHistogram and add tests for case with empty histogram
Fix case of merging TProfile with different limits when the first profile is empty
(the fix applied previously for bug #5509 was not applied to the TProfile)

Improve also tests for 2D and 3D profile
Fix out-of-bounds problem in TClass::EscapeChars

Increase the maximum size to 255 and make sure that the new, expanded string fix in the fixed length buffer.
This fixes ROOT-6239