This implements the relevant math typography rules described in the
Appendix G of the TeXbook. More precisely, for each atom
+ the class is computed by implementing rules 5 and 6 of Appendix G
+ the spacing is computed according to the table p. 170
This code is not used at this point.
This done according to the TeXbook. This class replaces the individual
isMathXXX() methods. The mathClass() method (currently unused) is
provided for the following insets:
* InsetMathChar (with a revised list of affected characters)
* InsetMathSymbol: the class is given by the `extra' field
Operators defined in lib/symbols (e.g. \log) are MC_OP
* InsetMathFrac is MC_INNER (except nicefrac and units)
* InsetDelimiters is MC_INNER
* InsetStackrel is MC_REL
* The class of InsetScript is the class of the last element of its
nucleus (yes, it is a hack, but doing it right is more work).
Remove the explicit spacing that was done in the different insets. The spacing
will be reintroduced properly in a forthcoming commit.
