This pull request includes fixes for a number of font issues in the 2.x milestone.
- Make U+222B (integral) stretchy in the STIX fonts (#1092 (closed))
- Remap
|to variant form in STIX (that has descender) and map variant to original form (#1154 (closed)) - Use U+007C and U+2016 for delimiters rather than U+2223 and U+2225 (#1175 (closed))
- Fix SVG font data for stretchy characters in the TeX font data-extras files (#1421 (closed))
- Alias U+2206 to U+0394 and remove incorrect U+2206 from SVG font files (#1418 (closed))
- Make height and depth of minus match that of plus (needed for TeX super/subscript algorithm to work properly), and adjust for that when it is used as an extender in stretchy characters (#1187 (closed)).
The last one affected all the web font files, in the HTML-CSS, SVG, and CommonHTML output, so it was extensive. This doesn't solve all the problems in the extra web font data files (there are many issues). I also didn't try to fix the scripts that were used originally to create the files, as I didn't want to waste time on that, as I think the whole web font approach needs to be rethought for v3.0. So these were edited by hand (we'll need to remember that for the future).