fix Issue 4899 - Ddoc: Warnings about stray parens do not include file and line numbers for module comments

Add ModuleDeclaration::loc and use it for "Stray paren" ddoc warning.
Merge pull request #2291 from 9rnsr/fix4899

Issue 4899 - Ddoc: Warnings about stray parens do not include file and line numbers for module comments