Documentation: Rename link macros

They can no longer end with "link", as explained in commit 5162e697 by
Dan McGee <dpmcgee@gmail.com> in the git repository:

    Documentation: rename gitlink macro to linkgit

    Between AsciiDoc 8.2.2 and 8.2.3, the following change was made to the stock
    Asciidoc configuration:

    @@ -149,7 +153,10 @@
     # Inline macros.
     # Backslash prefix required for escape processing.
     # (?s) re flag for line spanning.
    -(?su)[\\]?(?P<name>\w(\w|-)*?):(?P<target>\S*?)(\[(?P<attrlist>.*?)\])=
    +
    +# Explicit so they can be nested.
    +(?su)[\\]?(?P<name>(http|https|ftp|file|mailto|callto|image|link)):(?P<target>\S*?)(\[(?P<attrlist>.*?)\])=
    +
     # Anchor: [[[id]]]. Bibliographic anchor.
     (?su)[\\]?\[\[\[(?P<attrlist>[\w][\w-]*?)\]\]\]=anchor3
     # Anchor: [[id,xreflabel]]

    This default regex now matches explicit values, and unfortunately in this
    case gitlink was being matched by just 'link', causing the wrong inline
    macro template to be applied. By renaming the macro, we can avoid being
    matched by the wrong regex.

Signed-off-by: Karl Hasselström <kha@treskal.com>