* i387-nat.c: Include "i387-nat.h". Use regnum instead of regno

consistently for parameter names.  Fix comments accordingly.
(i387_supply_register): New function.
(i387_supply_fsave): Implement using i387_supply_register.
* i387-nat.h: Use regnum instead of regno consistently for
parameter names.  Fix comments accordingly.
(i387_supply_register): New prototype.