Clang: Extract TranslationUnitUpdater

...in preparation for concurrent processing of documents.

Parsing and reparsing is handled by TranslationUnit. Since we will do
this in a different thread, extract the core logic into the new class
TranslationUnitUpdater, so that we can prepare the necessary data for
the run and then later incorporate the results of the parse/reparse.

Change-Id: Ic9d936d193ee6795a755f0cfc38c0b2a7bd402cc
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/tools/clangbackend/ipcsource/clangbackendclangipc-source.pri

@@ -30,6 +30,7 @@ HEADERS += $$PWD/clangcodemodelserver.h \
     $$PWD/cursor.h \
     $$PWD/skippedsourceranges.h \
     $$PWD/clangtranslationunit.h \
+    $$PWD/clangtranslationunitupdater.h \
     $$PWD/clangtype.h \
     $$PWD/highlightingmark.h \
     $$PWD/highlightingmarks.h \
@@ -67,6 +68,7 @@ SOURCES += $$PWD/clangcodemodelserver.cpp \
     $$PWD/cursor.cpp \
     $$PWD/skippedsourceranges.cpp \
     $$PWD/clangtranslationunit.cpp \
+    $$PWD/clangtranslationunitupdater.cpp \
     $$PWD/clangtype.cpp \
     $$PWD/highlightingmark.cpp \
     $$PWD/highlightingmarks.cpp \