Uniform syntax for all pseudo-instructions

[flamewing]

Some pseudo-instructions have multiple allowed forms; e,g,:

• equ (spelled as constant in some targets)

  ; All of these are equivalent
  value1 equ 1
  value2 = 2
      equ value3,3

• set (spelled as eval in some targets)

  ; All of these are equivalent
  value1 set 1
  value2 = 2
      set value3,3

But not others:

• reg only supports myreg reg d0
• namereg only supports namereg s08,myreg (and note the inconsistency on register name placement compared to set and equ)
• label only supports mylabel label *; it should also accept label mylabel,*
• pseudo-instructions of some other targets might also benefit from this

function and macro are trickier, but it might be worth supporting the alternate syntax anyway.