[PATCH] line folding support

[rexy712]

Line folding is the ability for to hide or collapse a section of a file when you don't need to see it. All IDEs I've used have had this feature and it's the one thing I feel GNU nano has been missing when working from the terminal. It helps to keep the screen less cluttered when trying to focus. Folding lines is also useful when trying to work on two parts of a file at the same time, or when referencing something in a different section of the same file instead of jumping back and forth.

Almost a year ago, I was wondering about hacking line folding support into nano. Then I came across this bug #58199: [Wish] the ability to temporarily "fold" lines. This made me realize I wasn't the only one who wanted to see this feature, so I implemented it. These patches are the results.

I have been maintaining this patch for around 9 months on my own personal builds. I haven't seen any instability in a long time and feel it's time to submit to see if anyone else is interested or, more likely, has issues with my patches they'd want improved before considering it.

This patch is pretty massive, so I've also split it into multiple patches after finishing. So to be clear, these patches are not the order in which it was developed. But rather my attempt at a logical grouping of modifications to hopefully make my intent with some changes more clear. I'm also posting the full patch as a single file. This single file does not include the color patch. That way it doesn't get in the way of seeing other changes.

Thanks for your time,

rexy712

0000-Full-folding-support-in-one.patch
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0001-Add-the-basic-support-structure-for-the-folding-func.patch
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0002-Add-calls-to-UNFOLD_SEGMENT-in-existing-functions.patch
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0003-Modify-signatures-of-functions-to-be-modular-for-fur.patch
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0004-Modify-line-number-arithmetic-to-no-longer-assume-li.patch
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0005-Handle-all-the-more-complicated-modifications-to-exi.patch
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0006-Add-option-enable-folding-and-add-shortcut-for-foldi.patch
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0007-Add-colorization-to-folding-segments.patch
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