`-Wstring-conversion` and assert

[grandinj]

Bugzilla Link	43544
Version	unspecified
OS	All
CC	@stbergmann

Extended Description

It would be nice if the above warning would whitelist the common idiom

    assert(!"Unknown LibreOfficeKitCallbackType type.");

so I don't have to rewrite them all to

    assert(false && "Unknown LibreOfficeKitCallbackType type.");

which seems to work

:-)

(I'm testing this with clang trunk from about 4 weeks ago i.e. clang towards 10)