Since 8f628e05 changed the height and depth of the minus sign to match that of the plus sign (to match TeX's requirements for its usage), the use of U+2212 as a stretchy horizontal character is now causing alignment issues in some cases. This PR switches U+2013 (en-dash) for U+2212 in stretchy characters to avoid that problem in the MathJax TeX fonts.
Resolves issue #1686 (closed)