Use target pointer width rather than x86

[tgross35]

The code

astro-float/astro-float-num/src/defs.rs

Lines 11 to 33 in 891843d

	/// A word.
	#[cfg(not(target_arch = "x86"))]
	pub type Word = u64;
	/// Doubled word.
	#[cfg(not(target_arch = "x86"))]
	pub type DoubleWord = u128;
	/// Word with sign.
	#[cfg(not(target_arch = "x86"))]
	pub type SignedWord = i128;
	/// A word.
	#[cfg(target_arch = "x86")]
	pub type Word = u32;
	/// Doubled word.
	#[cfg(target_arch = "x86")]
	pub type DoubleWord = u64;
	/// Word with sign.
	#[cfg(target_arch = "x86")]
	pub type SignedWord = i64;

has a lot of code that is configured based on x86 or not(x86). Is there a reason that x86 is special, or could this instead use #[cfg(target_pointer_width = 64)]/#[cfg(target_pointer_width = 32)]?

[stencillogic]

Basically, the library only supports x64 and x86. Hence it uses just x86 and not(x86) here and there. It was tested for ARM once, but in general ARM is not supported at the moment.