undo wrong use of addblitFrom()

rendertext.lua did use addblitFrom() for rendering text - i.e. blitting
the letters to a BlitBuffer. However, it used intensity=1.0, which is
the same as doing a (faster, more efficient) blitFrom(). So use that
instead.

What was probably intented here is a different kind of blitting - using
the bitbuffer of the glyph as a mask.

frontend/ui/rendertext.lua

@@ -163,11 +163,11 @@ function RenderText:renderUtf8Text(buffer, x, y, face, text, kerning, bold, bgco
             if kerning and (prevcharcode ~= 0) then
                 pen_x = pen_x + face.ftface:getKerning(prevcharcode, charcode)
             end
-            buffer:addblitFrom(
+            buffer:blitFrom(
                 glyph.bb,
                 x + pen_x + glyph.l, y - glyph.t,
                 0, 0,
-                glyph.bb:getWidth(), glyph.bb:getHeight(), 1)
+                glyph.bb:getWidth(), glyph.bb:getHeight())
             pen_x = pen_x + glyph.ax
             prevcharcode = charcode
         end -- if pen_x < text_width