patch: init exponent for sim_fpu_class_zero

[Andrew Cagney]

> howdy.
> 
> in sim-fpu.c, the exponent is left undefined for zeros (sim_fpu_class_zero).
> 
> i am working on a port whose multiply and divide instructions check the 
> value of the operands' exponent and sign to determine overflow bits to set.  
> this is obviously not working when the exponent is undefined ;-).
> 
> i have verified that i can build the sim and gdb after my change (for
> powerpc-eabi).
> 
> ok to install?

Hmm, wierd,

> + 	  dst->normal_exp = 0;

of the possible values that is the most intuitive so yes.

Can you, separatly, commit/post a patch adding your self to the 
gdb/MAINTAINERS file under write after approva.

Andrew