LaTeX reader: More siunitx improvements. Closes #6658.

There's still one slight divergence from the siunitx behavior:
we get 'kg m/A/s' instead of 'kg m/(A s)'. At the moment I'm
not going to worry about that.

test/command/6658.md

@@ -1,15 +1,75 @@
 ```
-pandoc -f latex
-\SI{10.0 +- 3.3}{\ms}
+pandoc -f latex -t html
+\num{12345,67890}
+
+\num{1+-2i}
 
 \num{.3e45}
 
-\ang{+10;+3;}
+\num{1.654 x 2.34 x 3.430}
+
+\si{kg.m.s^{-1}}
+
+\si{\kilogram\metre\per\second}
+
+\si[per-mode=symbol]{\kilogram\metre\per\second}
+
+\si[per-mode=symbol]{\kilogram\metre\per\ampere\per\second}
+
+\numlist{10;20;30}
+
+\SIlist{0.13;0.67;0.80}{\milli\metre}
+
+\numrange{10}{20}
+
+\SIrange{0.13}{0.67}{\milli\metre}
+
+\ang{10}
+
+\ang{1;2;3}
+
+\ang{;;1}
+
+\ang{+10;;}
+
+\ang{-0;1;}
+
+\si{kg.m/s^2}
+
+\si{g_{polymer}~mol_{cat}.s^{-1}}
+
+\si{\kilo\gram\metre\per\square\second}
 
 \si{\gram\per\cubic\centi\metre}
+
+\si{\square\volt\cubic\lumen\per\farad}
+
+\si{\metre\squared\per\gray\cubic\lux}
+
+\si{\henry\second}
 ^D
-<p>10.0 ± 3.3 ms</p>
+<p>12345.67890</p>
+<p>1 ± 2i</p>
 <p>0.3 × 10<sup>45</sup></p>
-<p>10°3′</p>
-<p>g/cm<sup>3</sup></p>
+<p>1.654 × 2.34 × 3.430</p>
+<p>kg m s<sup>−1</sup></p>
+<p>kg m s<sup>−1</sup></p>
+<p>kg m/s</p>
+<p>kg m/A/s</p>
+<p>10, 20, &amp; 30</p>
+<p>0.13 mm, 0.67 mm, &amp; 0.80 mm</p>
+<p>10–20</p>
+<p>0.13 mm–0.67 mm</p>
+<p>10°</p>
+<p>1°2′3″</p>
+<p>1″</p>
+<p>10°</p>
+<p>-0°1′</p>
+<p>kg m/s<sup>2</sup></p>
+<p>g<sub>polymer</sub> mol<sub>cat</sub> s<sup>−1</sup></p>
+<p>kg m s<sup>−2</sup></p>
+<p>g cm<sup>−3</sup></p>
+<p>V<sup>2</sup> lm<sup>3</sup> F<sup>−1</sup></p>
+<p>m<sup>2</sup> Gy<sup>−1</sup> lx<sup>3</sup></p>
+<p>H s</p>
 ```