Sets the family name field of a font description, without copying the string.
This is like [method@Pango.FontDescription.set_family], except that no copy of
family is made. The caller must make sure that the
string passed in stays around until this has been freed or the name is set again. This function can be used if
family is a static string such as a C string literal, or if this is only needed temporarily.
a string representing the family name