[intro.refs, intro.defs] Update ISO 80000-2:2009 to :2019, change "and" to comma

Author: tkoeppe

source/intro.tex

@@ -48,8 +48,7 @@
 \item ISO/IEC/IEEE 9945:2009/Cor 2:2017, \doccite{Information Technology --- Portable Operating System Interface
 (POSIX\textregistered) Base Specifications, Issue 7 --- Technical Corrigendum 2}
 \item ISO/IEC 60559:2020, \doccite{Information technology --- Microprocessor Systems --- Floating-Point arithmetic}
-\item ISO 80000-2:2009, \doccite{Quantities and units --- Part 2:
-Mathematical signs and symbols to be used in the natural sciences and technology}
+\item ISO 80000-2:2019, \doccite{Quantities and units --- Part 2: Mathematics}
 % Other international standards.
 \item Ecma International, \doccite{ECMAScript
 \begin{footnote}
@@ -72,7 +71,7 @@
 \indextext{definitions|(}%
 For the purposes of this document,
 the terms and definitions
-given in ISO/IEC 2382 and ISO 80000-2:2009,
+given in ISO/IEC 2382, ISO 80000-2:2019,
 and the following apply.
 
 \pnum