Extended mnemonics of branch instructions

The assembler supports extended mnemonics for different types of Register instructions.

The assembler supports extended mnemonics for Branch Conditional, Branch Conditional to Link Register, and Branch Conditional to Count Register instructions. Since the base mnemonics for all the Branch Conditional instructions are in the com assembly mode, all of their extended mnemonics are also in the com assembly mode.

Extended mnemonics are constructed by incorporating the BO and BI input operand into the mnemonics. Extended mnemonics always omit the BH input operand and assume its value to be 0b00.