Add mnemonic constants:

kHAlignLeft=10, kHAlignCenter=20, kHAlignRight=30,
kVAlignBottom=1, kVAlignCenter=2, kVAlignTop=3

They allow to write: object->SetTextAlign(kHAlignLeft+kVAlignTop)
provide symbolic values for different styles as suggested here:
https://sft.its.cern.ch/jira/browse/ROOT-4910
Protection added in UnZoom
Fix https://sft.its.cern.ch/jira/browse/ROOT-4516
The option "A" in the `Draw()` was not cleaning properly the current pad.
Started working on integrating IgProf in PROOF
PROOF: tag identifying additional logfiles

Tags are now used for the Valgrind and IgProf wrappers, generating
additional logfiles. They are appended to the "ordinal" number both for
the master line and the workers lines. Appending tags to ordinals also
incidentally fixes a bug leading to having the additional logfile
concatenated to the ordinary logfile while getting the first.
Fixed PROOF pct of completion when getting logs
No newline in PROOF logfiles retrieval progress
Added PROOF logfiles preprocessing before sending
Added quotes for igprof cmd in PROOF-Lite
PROOF GUI support for log filtering via pipe cmd
Some debug in PROOF log retrieval
PROOF: automatic igprof-analyse for IgProf pp logs
No bloating IgProf output and clearer profile type

Now the tag to invoke IgProf performance profiling is "igprof-pp" and
no longer "igprof" alone. Leaves some space for adding IgProf memory
profiling.
Add missing forward declaration
Fix warning
fix name completion for instances
   Fix work-distribution issue in multi-master setups with masters having no active worker.
  In TVirtualPacketizer.h:
  Add new virtual method AssignWork to be used to add work to an existing packetizer on
  the fly. This is used while packetizing across submasters.
  In TVirtualPacketizer.cxx:
  Do not start the progress reporting on submaster (progress is under control of top masters).
  In TPacketizerUnit:
  First implementation of the new method AssignWork .
Synchronize TPacketizerUnit with master