Only modify the loca table is there is such a table.
Separate out the logic of computing advanceWidthMax from minLeftSideBearing, minRightSideBearing, and xMaxExtent for minimal fonts.
Fixup hhea recalc after 9222b8ef93fd6b41f9c4dcf152593cd0c80f0ba4
Fixup ttx file-name mangling after eac107f1