Add return value to LoadText(), Declare() (ROOT-5698).

(cherry picked from commit 901dc0b3b1b7ae0d958474f6517a4737c6729d48)
Do not mark as Unloaded object refering to decl that will not be unloaded
Mark TClass::ResetClassInfo(Long_t tagnum) as deprecated
Only update the TClass if the definition is being unloaded.

And not when it is 'only' a forward declaration
Improve state TClass' state transition when loading or unloading ClassInfos.

In ResetClassInfo, avoid forgetting that a TClass was created by a dictionary.
In SetClassInfo, also transition the state when the ClassInfo is found but invalid.
In SetClassInfo, properly set the state if we have 'only' StreamerInfos as a source of info.
In ResetClassInfo, do not use SetClassInfo.

Just delete the ClassInfo and rely on the TClass' state to be accurate/good enough to
recreate the ClassInfo when needed.

This (and the related commits) fixes ROOT-6804 and ROOT-6806
Write empty pchs if the user asks to and consider this in TCling
Do not generate fwd decl payload nor autoparse keys when pcm is empty.

This allows to gain memory and runtime at library load. The improvement
has not a tremendous impact on long running jobs but it is clearly
visible at startup. If the payload is not present parsing is avoided.
Re-enable injection of autoparse keys for non-stage 1, non-in-pch dictionaries
tutorials/proof/event.par: update Makefile, Makefile.arch
Add autoloading of selected enums

is an enum is selected, it becomes an autoload key. The mechanism
works for queries to the typesystem via TEnum::GetEnum and not for
the interpreter.
In this latter case, presently, the limitation is the absence of the
concept of enum fwd declaration. We cannot hook on the incomplete type
error clang would emit.
Improve protoclasses by using now a single char for storing three boolean flags  for the TProtoRealData(Thanks to Philippe)
Remove SetIsLoaded from TListOfDataMembers and add a new constructor from a generic lit of Data members
Yosemite and NSApplication.

Use sharedApplication instead of NSApp.
Fix initialisation of class data members in the new TListOfDataMembers constructor
Fix  a memory leak in fftw classes (ROOT-6838), thanks to Stephan Huber
Add possibility in DrawCopy to maintain the same name of the histogram. This fixes ROOT-6557
Add selected enums as keys in the capabilities files
Delay Oracle donations until they are needed.
Added test dependency to avoid race condition
Avoid to autoparses on inclusion directives