GTask: convert long desc to markdown

Use markdown sections and lists here.
GSocketClient: convert docs to markdown
GSimpleProxyResolver: convert docs to markdown
GMenuModel: Convert docs to markdown
GDBusProxy: Convert docs to markdown
GIcon: Convert docs to markdown
GDBusConnection: Convert docs to markdown

And straighten out capitalization across the file.
gdbusnameowning: Convert docs to markdown
GApplication: Convert docs to markdown
testutils: Convert docs to markdown

Convert lists to markdown.
gthread: Convert docs to markdown

Convert lists to markdown syntax.
GVariant: convert docs to markdown

Convert lists to markdown syntax, and remove a lot of <literal>.
GVariantType: convert docs to markdown

Convert lists to markdown syntax, and remove lots of <literal>.
kqueue: Don't use doc comments

This is not public API, so no need to confuse gtk-doc by
documentation that it needs to ignore. Also, no need for
markup in here.
gconvert: Convert docs to markdown

In particular, we convert sections and lists to markdown syntax
here.
GDateTime: Convert docs to markdown

In particular convert sections and lists to markdown syntax.
GError: Convert docs to markdown

In particular, convert lists to markdown syntax.
fileutils: Convert docs to markdown

In particular, convert lists to markdown syntax.
ggettext: Convert docs to markdown

In particular, convert lists to markdown syntax.
GIOChannel: remove unneeded markup from the docs