Clang: clean up unit handling.

- Use a QSharedPointer instead of an explicitly shared pointer.
- Remove the LiveUnitManager.

Change-Id: I05bf32c1f77c17f42ee1da39f1353cff580fa6eb
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/clangcodemodel/clangcodemodel.qbs

@@ -163,8 +163,6 @@ QtcPlugin {
         "diagnostic.h",
         "fastindexer.cpp",
         "fastindexer.h",
-        "liveunitsmanager.cpp",
-        "liveunitsmanager.h",
         "pchinfo.cpp",
         "pchinfo.h",
         "pchmanager.cpp",