Fixes https://github.com/fonttools/fonttools/issues/2949 - If there are no marked glyphs in an "ignore" statement, issue a warning. The spec disallows this but makeotf allows it. It is most likely a typo, so a warning is warranted. - Mark the first glyph not all the glyphs, this matches makeotf. - In asFea() always mark the input glyph. - Udpate the tests.