Now that all our supported compilers know char16_t, we no longer need
QStringViewLiteral, whose only purpose in life was to turn u"" into
L"" for MSVC < 2015.
Change-Id: I25a094fe7992d9d5dbeb4a524d9e99e043dcb8ce
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>