Cpp{Tools,Editor}: Respect multi-QChar code points when handling identifiers

* Consolidate code dealing with C++ identifiers into cpptoolsreuse.h
* Handle code points that are represented with two QChars

Change-Id: I4fb4435aa539f65d88598cac0b50629f33f32440
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/plugins/cpptools/cppcompletionassistprovider.cpp

@@ -29,6 +29,8 @@
 
 #include "cppcompletionassistprovider.h"
 
+#include "cpptoolsreuse.h"
+
 #include <cppeditor/cppeditorconstants.h>
 
 #include <cplusplus/Token.h>
@@ -59,6 +61,11 @@ bool CppCompletionAssistProvider::isActivationCharSequence(const QString &sequen
     return false;
 }
 
+bool CppCompletionAssistProvider::isContinuationChar(const QChar &c) const
+{
+    return isValidIdentifierChar(c);
+}
+
 int CppCompletionAssistProvider::activationSequenceChar(const QChar &ch,
                                                         const QChar &ch2,
                                                         const QChar &ch3,