CppEditor: Fix MSVC warning

MSVC2015-amd64 warns about size_t -> int implicit conversion

Change-Id: I60ec63cd50b9a48d96b838237b2e926b3d6ace5b
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/cppeditor/cppeditor.cpp

@@ -521,7 +521,7 @@ sourceLocationsToExtraSelections(const std::vector<SourceLocationContainer> &sou
     const auto textCharFormat = occurrencesTextCharFormat();
 
     QList<QTextEdit::ExtraSelection> selections;
-    selections.reserve(sourceLocations.size());
+    selections.reserve(int(sourceLocations.size()));
 
     auto sourceLocationToExtraSelection = [&] (const SourceLocationContainer &sourceLocation) {
         QTextEdit::ExtraSelection selection;