[lex.ext] Fully-qualify std::size_t in example.
[gram] Rebuild grammar after eb18f34d.
CWG1705 Unclear specification of “more specialized”

Italicize defined term 'more specialized'. For clarity, switch class template
partial specializations from defining 'at least as specialized as' to defining
'more specialized than', since the latter term is the one used everywhere else
in the standard (excluding within the definition of 'at least as specialized
as' for function templates).
CWG1708 overly-strict requirements for names with C language linkage
CWG1710 Missing template keyword in class-or-decltype