Use Clang's FixItHints to correct expressions with "trivial" mistakes (e.g. "." for "->".)
This feature is controlled by an expression command option, a target property and the
SBExpressionOptions setting. FixIt's are only applied to UserExpressions, not UtilityFunctions,
those you have to get right when you make them.
This is just a first stage. At present the fixits are applied silently. The next step
is to tell the user about the applied fixit.