Reference (section label): [temp.deduct.guide]

Issue description: CWG2707 added the missing requires-clause to the grammar for deduction-guide, but added it in a position that is inconsistent with function declarations. Since the grammar for deduction guides is supposed to match that of other declarator-based declarations, the requires-clause should be at the end.

Suggested resolution:

Change in [temp.deduct.guide]/1:

deduction-guide:

• explicit-specifier_opt template-name ( parameter-declaration-clause ) requires-clause_opt -> simple-template-id requires-clause_opt ;