Clang: Provide tooltips

This includes also the query data for the help system (F1) for an
identifier under cursor.

Regressions (libclang changes necessary):
 - Function signatures do not contain default values.
 - Aliases are not resolved for/at:
   - template types
   - qualified name of a type

Fixes/Improvements:
 - Resolve "auto"
 - On a template type, show also the template parameter.
 - For a typedef like
     typedef long long superlong;
   the tooltip was "long long superlong", which was confusing.
   Now, "long long" is shown.

New:
 - Show first or \brief paragraph of a documentation comment.
 - Show size of a class at definition.
 - Show size of a field member in class definition.

Task-number: QTCREATORBUG-11259
Change-Id: Ie1a07930d0e882015d07dc43e35bb81a685cdeb8
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/clangcodemodel/clangcodemodel.pro

@@ -30,6 +30,7 @@ SOURCES += \
     clangfixitoperationsextractor.cpp \
     clangfollowsymbol.cpp \
     clangfunctionhintmodel.cpp \
+    clanghoverhandler.cpp \
     clangtokeninfosreporter.cpp \
     clangmodelmanagersupport.cpp \
     clangpreprocessorassistproposalitem.cpp \
@@ -66,6 +67,7 @@ HEADERS += \
     clangfixitoperationsextractor.h \
     clangfollowsymbol.h \
     clangfunctionhintmodel.h \
+    clanghoverhandler.h \
     clangisdiagnosticrelatedtolocation.h \
     clangmodelmanagersupport.h \
     clangpreprocessorassistproposalitem.h \