any given register table.
(register_name): Pass appropriate table and size to reg_name_search.
(system_register_name): New function.
(SYSREG_NAME_CNT): Define.
(md_assemble): Handle operands which are system registers.
Still working on the parser..
opcode doesn't want a register, then we don't have a match.
(md_assemble): Get size of the instruction from the opcode table.
So we choose the right opcode and so that we get the sizes right.
