Some fixes to my pull request for other underlines

[AhoyISki]

A while ago, I sent a pull request to add undercurls and other types of underline to crossterm.
I just realized that I forgot to include methods for doing that to styles.

Now, Stylize will include the double_underlined, undercurled, underdotted and underdashed methods.

This commit also makes the printing of these underlines slightly faster by changing the check for "4:{}" to be just one if statement instead of two.

It also implements Clone and Copy for SetCursorStyle, I did that a while ago though... so I don't really remember why.

[TimonPost]

can you elaborate on this check change? Before there was a range check of 5..9 and now everything above 23?

[AhoyISki]

This was changed to reduce the number of checks.

Previously, the special underlines were in the middle of the enum, so you had to check for a lower and an upper bound whenever they came up.

Now, I moved them to the end, so you only have to check for a lower bound.

[AhoyISki]

Hey, just asking real quick, but are there plans for merging this PR? Any other concerns with its contents? I'm asking because I have a crate that depends on my github version, and it is not possible to depend on a github version when publishing to crates.io

[joshka]

23 makes it difficult to work out how this code works and makes the code fragile to changes. Would this work better? It still assumes that the underline types are sequential, but makes it easier to understand what bounds are in play here.

Suggested change

	if (self as usize) > 23 {
	if (self as usize >= Self::DoubleUnderlined as usize) && (self as usize <= Self::Underdashed as usize) {

[AhoyISki]

Yes, that is more clear, but you can remove the second check since the maximum value is known to be <= (Self::Underdashed as usize).

[joshka]

That's safe unless you add some other variant at the end, or you move the options back somewhere within the enum like they were originally. Putting upper and lower bounds on the check makes it clear that the rationale is that these options are contiguous in the enums variants. I'd guess that having this check is unlikely to be on the hot path (and is probably even compiled out in a release build).

[joshka]

23 makes it difficult to work out how this code works and makes the code fragile to changes. Would this work better? It still assumes that the underline types are sequential, but makes it easier to understand what bounds are in play here.

Suggested change

	if (self as usize) > 23 {
	if (self as usize >= Self::DoubleUnderlined as usize) && (self as usize <= Self::Underdashed as usize) {

[joshka]

Suggested change

	return "4:".to_string() + SGR[self as usize].to_string().as_str();
	return format!("{}:{}", Self::Underlined as usize, SGR[self as usize]);