Change '@'s priority spacing

The old value is based on Mathematica's usage as prefix function call (f @ x === f[x]). However, in math, it might be used as some quantity wrt to another quantity as in "1.050 g/cm3 @ 15 °C" (from Wikipedia). Hence, it should be lower than multiplication but higher than plus.

Author: NSoiffer

unicode.xml

@@ -1216,7 +1216,7 @@ Barbara Beeton for the STIX project
             <desc>=commercial at</desc>
          </entity>
          <font name="ptmr7t" pos="64"/>
-         <operator-dictionary priority="825" form="infix" lspace="1" rspace="1"/>
+         <operator-dictionary priority="360" form="infix" lspace="3" rspace="3"/>
          <description unicode="1.1">COMMERCIAL AT</description>
       </character>
       <character id="U00041" dec="65" mode="text" type="other">