Use rootcling to generate rootmaps during the root build

To achieve this goal the following changes were applied:
1) rlibmap is reduced to a no-op with a nice deprecation message.
The return value is zero not to break build systems which may
rely on it. This will be transformed to an error in beta 2.
rlibmap will be removed in beta 3.
2) The build systems were updated in order to leverage rootcling
for the rootmap generation, basically adding 2 flags, -rmf and -rml.
3) Rootcling has a new option, -r which is on the same footing of
-f but it tells the system to ignore the dictionary generation.
When -r is present rootcling becomes a tool to generate rootmaps
(and capability files).

At the moment the makefile build does not properly account for
rootmaps as targets, i.e. a deleted/modified rootmap will trigger
a no-op rlibmap. A forthcoming commit will fix this behaviour.
Make rootmaps a target for libHist
80col, spaces.
Fixes issue ROOT-5813 (CMake)
Fix test after FillRandom changes
Remove check for existing dictionary headers

given that dictionary headers are not created anymore since ~1month
Limit the search to just the list of modules

This avoid picking up by mistake the content of sub-directory that
are, for example, separate out-of-source builds (e.g. with different
compiler version or optimization level)
Fix a typo in the doc (ROOT-5223)
Aclic: generate rootmaps with rootcint if they are requested

the rootmapfile was created within the TSystem::CompileMacro function
assuming the "old" rootmapfile format. This upgrade allows to have
a single producer of rootmapfiles: rootcling.
speed-up TVector3::Unit (see ROOT-5302)
cleanup of offset calculations by always using (derived, base) in the interfaces and by explicit naming; also removed a workaround, and this closes ROOT-5781
Fix iterators.
Print all macros instead one by one.
Add --text to diff not only text files and treat all files as text.
Improve and move the implementation of removeMacro.
Improve style.
Improve uncaching of unloaded files.

*Merge PreVisitDecl and PreVisitMacro and rename to CollectFilesToUncache.
*Add FID to the transaction storing the memory buffer file ID caused the
transaction.
Add error recovery and unloading tests.
Cleanup the lookup tables of the first non-transparent parent of an enum constant.
Improve style.