When applying small size and big outline and underline and strike through, it happens nasty corner cases.
that would make the code crash if there were not boundary check.


- we have already increased the limit for underline style set by something like this:
 font->height = SDL_max(font->height, bottom_row);

I added the same update of font->height also for strike-through. 
(big outline makes the lines thickness be greater than height/2 and then bottom_row writes than surface height).

- Then now, there is a circular dependency, because: 
  TTF_strikethrough_top_row() returns (height/2)
  bottom_row = TTF_strikethrough_top_row() + thickness
  new height is SDL_max(font->height, bottom_row);
  when it renders, TTF_strikethrough_top_row() returns (new_height/2). which can write out of bounds.

So I just move the strike/underline_to_row in the font structure. They are initialized when style changes.
And not recomputed any more each time it renders.


We just need to make sure the TTF_Size() is set correctly. Since the line can be of any thickness.
it's inside a boundary box of miny=0 maxy=font->height at yoffset 0. 
We can virtually treat it as glyph by adding the same check:
  maxy = SDL_max(maxy, glyph->yoffset + glyph->maxy - glyph->miny);
ie
  maxy = SDL_max(maxy, font->height);
finally simply initializing
  maxy = font->height;

and also the height surface 
  *h = SDL_max(font->height, maxy - miny); 
as maxy >= font->height, and miny <=0, becames only:
  *h = (maxy - miny);


In the modification: 
- create underline/strikethrough_top_row into TTF_FONT structure, and remove TTF_underline/strikethrough_top_row() private functions.
- remove the boundary check of DrawLines
- merge together TTF_drawLine_Solid() & TTF_drawLine_Shaded() as there are similar. (color 1, vers NUMGRAY - 1)
- inline TTF_initLineMectrics just initializing two vars.
- remove a duplicate "maxx = SDL_max(maxx, x + glyph->advance);"