ClangSupport: override indentationSample()
ILanguageSupport::indentationSample() is used in a single place: CustomScriptPlugin::computeIndentationFromSample(), which in turn is used only in CustomScriptPlugin::indentation(). When indentationSample() returns an empty string (as the base class implementation does), CustomScriptPlugin::indentation() fails and returns invalid Indentation. f31d32f4 removed CppLanguageSupport, which was the only class that overrode indentationSample(). Not copying this override into ClangSupport was probably a mistake. This commit copies the last version of CppLanguageSupport::indentationSample() into ClangSupport::indentationSample(). The copied sample matches the example in the documentation for ILanguageSupport::indentationSample().