[dcl.spec.general,dcl.fct.spec] Clarify duplication of decl-specifiers

Author: jensmaurer

source/declarations.tex

@@ -418,9 +418,9 @@
 same type.
 
 \pnum
-Each \grammarterm{decl-specifier}
-shall appear at most once in a complete \grammarterm{decl-specifier-seq},
-except that \tcode{long} may appear twice.
+At most one of each of the \grammarterm{decl-specifier}s
+\keyword{friend}, \keyword{typedef}, or \keyword{inline}
+shall appear in a \grammarterm{decl-specifier-seq}.
 At most one of
 the \keyword{constexpr}, \keyword{consteval}, and \keyword{constinit} keywords
 shall appear in a \grammarterm{decl-specifier-seq}.
@@ -651,6 +651,9 @@
 A
 \grammarterm{function-specifier}
 can be used only in a function declaration.
+At most one \grammarterm{explicit-specifier} and
+at most one \keyword{virtual} keyword shall appear in
+a \grammarterm{decl-specifier-seq}.
 
 \begin{bnf}
 \nontermdef{function-specifier}\br