C++: clean-up CppCompletionAssist.

This is step 1 of 2 for merging the various provider factories into a
single class. Merging has the advantage that selecting based on editor
(content) mime-type only has to select one class, instead of re-doing
the selection for each class separately.

Change-Id: I11f815151bd4769ae6028b636793d6a80d02e202
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/cpptools/cpptools.pro

@@ -32,7 +32,6 @@ HEADERS += completionsettingspage.h \
     doxygengenerator.h \
     commentssettings.h \
     symbolfinder.h \
-    cppcompletionsupport.h \
     cpphighlightingsupport.h \
     cpphighlightingsupportinternal.h \
     cppchecksymbols.h \
@@ -77,7 +76,6 @@ SOURCES += completionsettingspage.cpp \
     doxygengenerator.cpp \
     commentssettings.cpp \
     symbolfinder.cpp \
-    cppcompletionsupport.cpp \
     cpphighlightingsupport.cpp \
     cpphighlightingsupportinternal.cpp \
     cppchecksymbols.cpp \