x86-syntax: Add syntax for flags registers

[langston-barrett]

It would be useful to have syntax for the following registers:

macaw/x86_symbolic/src/Data/Macaw/X86/Symbolic/Regs.hs

Lines 266 to 300 in 2560988

	-- | Carry flag
	cf :: Ctx.Index (MacawCrucibleRegTypes M.X86_64) C.BoolType
	cf = Ctx.natIndex @CF
	-- | Parity flag
	pf :: Ctx.Index (MacawCrucibleRegTypes M.X86_64) C.BoolType
	pf = Ctx.natIndex @PF
	-- | Auxiliary carry flag
	af :: Ctx.Index (MacawCrucibleRegTypes M.X86_64) C.BoolType
	af = Ctx.natIndex @AF
	-- | Zero flag
	zf :: Ctx.Index (MacawCrucibleRegTypes M.X86_64) C.BoolType
	zf = Ctx.natIndex @ZF
	-- | Sign flag
	sf :: Ctx.Index (MacawCrucibleRegTypes M.X86_64) C.BoolType
	sf = Ctx.natIndex @SF
	-- | Trap flag
	tf :: Ctx.Index (MacawCrucibleRegTypes M.X86_64) C.BoolType
	tf = Ctx.natIndex @TF
	-- | Interrupt enable flag
	if_ :: Ctx.Index (MacawCrucibleRegTypes M.X86_64) C.BoolType
	if_ = Ctx.natIndex @IF
	-- | Direction flag
	df :: Ctx.Index (MacawCrucibleRegTypes M.X86_64) C.BoolType
	df = Ctx.natIndex @DF
	-- | Overflow flag
	of_ :: Ctx.Index (MacawCrucibleRegTypes M.X86_64) C.BoolType
	of_ = Ctx.natIndex @OF

This should be as simple as adding a few more cases here:

macaw/macaw-x86-syntax/src/Data/Macaw/X86/Symbolic/Syntax.hs

Line 114 in 2560988

LCSA.AtomName _ -> empty

and some lines to this test-case:

macaw/macaw-x86-syntax/test-data/get-regs.cbl

Line 1 in 2560988

(defun @id ((regs X86Regs)) X86Regs

We should be sure to update the documentation as well:

https://github.com/GaloisInc/macaw/blob/2560988c937eed393e22fdf14618657c8e8f60aa/macaw-x86-syntax/README.md

Checklist:

• Add syntax
• Modify test
• Add docs