[DOC] Use RDoc link style for links in the same class/module

I used this regex:

(?<=\[)#(?:class|module)-([A-Za-z]+)-label-([A-Za-z0-9\-\+]+)

And performed a global find & replace for this:

rdoc-ref:$1@$2

struct.c

@@ -1568,13 +1568,13 @@ rb_struct_dig(int argc, VALUE *argv, VALUE self)
  *
  *  Here, class \Struct provides methods that are useful for:
  *
- *  - {Creating a Struct Subclass}[#class-Struct-label-Methods+for+Creating+a+Struct+Subclass]
- *  - {Querying}[#class-Struct-label-Methods+for+Querying]
- *  - {Comparing}[#class-Struct-label-Methods+for+Comparing]
- *  - {Fetching}[#class-Struct-label-Methods+for+Fetching]
- *  - {Assigning}[#class-Struct-label-Methods+for+Assigning]
- *  - {Iterating}[#class-Struct-label-Methods+for+Iterating]
- *  - {Converting}[#class-Struct-label-Methods+for+Converting]
+ *  - {Creating a Struct Subclass}[rdoc-ref:Struct@Methods+for+Creating+a+Struct+Subclass]
+ *  - {Querying}[rdoc-ref:Struct@Methods+for+Querying]
+ *  - {Comparing}[rdoc-ref:Struct@Methods+for+Comparing]
+ *  - {Fetching}[rdoc-ref:Struct@Methods+for+Fetching]
+ *  - {Assigning}[rdoc-ref:Struct@Methods+for+Assigning]
+ *  - {Iterating}[rdoc-ref:Struct@Methods+for+Iterating]
+ *  - {Converting}[rdoc-ref:Struct@Methods+for+Converting]
  *
  *  === Methods for Creating a Struct Subclass
  *