These are currently initialized in a [[gnu::constructor]], which has a
weird initialization order. These constructors are invoked before main()
and, incidentally, before any user-defined default constructors of the
static strings they are initializing.
This will become an issue when these strings are ported to FlyString,
which has a user-defined default constructor. In that scenario, when the
FlyString constructor is executed after the [[gnu::constructor]], the
strings will be "reset" to the empty string.
Instead of relying on a non-standard compiler extension here, let's just
initialize these strings explicitly during main-thread VM creation, as
this now happens in WebContent's main().
DeprecatedFlyString relies heavily on DeprecatedString's StringImpl, so
let's rename it to A) match the name of DeprecatedString, B) write a new
FlyString class that is tied to String.
There are a whole bunch of SVG attributes, and we shouldn't mix them in
with the HTML attributes. This patch adds some of them to the new
namespace, but there are more to be added. :^)