Only left sides of wide glyphs are 2 columns

At various places in rendering and rasterizing, we advance two
columns upon encountering a wide glyph. When dealing with a
single plane, this is always correct, because we're always
hitting the first column of the multicolumn glyph. Once multiple
planes are brought into play, though, we can very much hit the
second column of said glyph, in which case we mustn't advance
two columns, but only one. Resolves #474 by way of #475. w00t!

src/lib/render.c

@@ -307,7 +307,7 @@ paint(ncplane* p, cell* lastframe, struct crender* rvec,
           }
           crender->p = p;
           targc->attrword = vis->attrword;
-        }else if(cell_double_wide_p(vis)){
+        }else if(cell_wide_left_p(vis)){
           cell_set_wide(targc);
         }
       }
@@ -355,7 +355,7 @@ fprintf(stderr, "POOL: %p NC: %p SRC: %p\n", pool->pool, nc, crender->p);
 }*/
         if(cellcmp_and_dupfar(pool, prevcell, crender->p, targc)){
           crender->damaged = true;
-          if(cell_double_wide_p(targc)){
+          if(cell_wide_left_p(targc)){
             ncplane* tmpp = crender->p;
             ++crender;
             crender->p = tmpp;
@@ -846,7 +846,7 @@ notcurses_rasterize(notcurses* nc, const struct crender* rvec){
         // here. no updates are performed to elision state nor lastframe.
         ++nc->stats.cellelisions;
         ++needmove;
-        if(cell_double_wide_p(srccell)){
+        if(cell_wide_left_p(srccell)){
           ++needmove;
           ++nc->stats.cellelisions;
         }
@@ -964,7 +964,7 @@ fprintf(stderr, "RAST %u [%s] to %d/%d\n", srccell->gcluster, egcpool_extended_g
 }*/
         ret |= term_putc(out, &nc->pool, srccell);
       }
-      if(cell_double_wide_p(srccell)){
+      if(cell_wide_left_p(srccell)){
         ++x;
       }
 //fprintf(stderr, "damageidx: %ld\n", damageidx);