Underline and overline need to clear glyph ascenders and descenders

[r12a]

Indian language text has some signs called as Matras which sometimes join above the shirorekha or below the normal baseline.

Applications should ensure that the underline and overline when getting rendered, should adaquetly be taken into consideration. Chrome browser seemed to be perfectly rendering the underline and overline feature by breaking the same where a matra/vowel sign occurs. Firefox also handles it a bit differently by appropriately lowering or heightening the respective lines.

[r12a]

The first comment in this issue contains text that will automatically appear in the Tamil gap-analysis document as a subsection with the same title as this issue. Any edits made to that comment will be immediately available in the document. Proposals for changes or discussion of the content can be made in comments below this point.

[r12a]

Closing in favour of #90