Same functionality as gda.holder.Holder.setValue except that it uses a string representation
of the value to set, which will be converted into a GValue first (using default data handler if
dh is null).
Note1: if value is null or is the "NULL" string, then holder's value is set to null.
Note2: if holder can't accept the value value, then this method returns FALSE, and holder will be left
in an invalid state.
Same functionality as gda.holder.Holder.setValue except that it uses a string representation of the value to set, which will be converted into a GValue first (using default data handler if dh is null).
Note1: if value is null or is the "NULL" string, then holder's value is set to null. Note2: if holder can't accept the value value, then this method returns FALSE, and holder will be left in an invalid state.