[simd.general, bibliography] Add SIMD acronym explanation and bibliographic reference (#7504)

To the existing Note at the beginning of [simd.general],
add text that unpacks the SIMD acronym and refers to Flynn 1966.

Add bibliography entry for Flynn 1966, the paper that introduced what
later became known as "Flynn's Taxonomy."  This classifies parallel
computer hardware as SISD, SIMD, MISD, or MIMD.

Author: mhoemmen

source/back.tex

@@ -86,6 +86,10 @@
   Roldan Pozo, Karin Remington, and R.\ Client Whaley,
   \doccite{An Updated Set of Basic Linear Algebra Subprograms (BLAS)}.
   ACM Trans.\ Math.\ Soft., Vol.\ 28, Issue 2, 2002.
+\bibitem{flynn-taxonomy}
+  Michael J.\ Flynn,
+  \doccite{Very High-Speed Computing Systems}.
+  Proceedings of the IEEE, Vol.\ 54, Issue 12, 1966.
 \end{thebibliography}
 
 % FIXME: For unknown reasons, hanging paragraphs are not indented within our

source/numerics.tex

@@ -16088,6 +16088,8 @@
 The intent is to support acceleration through data-parallel execution resources
 where available, such as SIMD registers and instructions or execution units
 driven by a common instruction decoder.
+SIMD stands for ``Single Instruction Stream -- Multiple Data Stream'';
+it is defined in Flynn 1966\supercite{flynn-taxonomy}.
 \end{note}
 
 \pnum