Tracking issue for potential breaking changes

[cuviper]

num-traits is somewhat of a de facto stable crate. Since these traits are often found in the public API of other crates, we really want to avoid the sort of ecosystem split that a breaking-change semver bump might cause.

Nevertheless, it's a good idea to track what breaking changes we might want to make someday, now found in the list below. Links are included to postponed issues, which often have more details. They will be closed in the meantime, but discussion can continue.

• Remove default epsilon implementation for Float Remove default epsilon implementation for Float #4
• Num::FromStrRadixErr should have Trait bound Num::FromStrRadixErr should have Trait bound #6
• More features for Float More features for Float #8
• All bit twiddling functions in num::traits::PrimInt should take or return usize instead of u32 All bit twiddling functions in num::traits::PrimInt should take or return usize instead of u32 #14
• std::num::Checked{Add,Sub,Mul,Div} should have type parameters std::num::Checked{Add,Sub,Mul,Div} should have type parameters #15
• Use Mul by reference in pow Use Mul by reference in pow  #18
• Make the Float trait depend on FloatConst. Make the Float trait depend on FloatConst. #20
• Add Default, Display, and Debug trait bounds to PrimInt Add Default, Display, and Debug trait bounds to PrimInt #44
• Easy conversions between Signed and Unsigned Easy conversions between Signed and Unsigned #46
• Blanket impl for Real trait prevents parameterized implementations. Blanket impl for Real trait prevents parameterized implementations. #49
• Functions to distinguish signaling from non-signaling NaN's Functions to distinguish signaling from non-signaling NaN's #51
• Bound FloatCore by Bounded? Bound FloatCore by Bounded? #55
• Implement traits for Reverse (rust 1.19+) impl Bounded for Reverse #65
• Make One::is_one a required method and remove its Self: PartialEq Add method is_one to One trait #5 (comment)
• LowerBounded and UpperBounded (Add LowerBounded/UpperBounded traits #210) should be super-traits of Bounded