Don't consider space as real space when there is an extra spacing (bug 931481)

- it aims to fix https://bugzilla.mozilla.org/show_bug.cgi?id=931481;
 - real space chars are pushed in the chunk but when there is an extra spacing, the next char position must be compared with the previous one;
 - for example, an extra spacing can cancel a space so visually there are no space.

src/core/evaluator.js

@@ -2573,7 +2573,8 @@ class PartialEvaluator {
           (i === 0 ||
             i + 1 === ii ||
             glyphs[i - 1].unicode === " " ||
-            glyphs[i + 1].unicode === " ")
+            glyphs[i + 1].unicode === " " ||
+            extraSpacing)
         ) {
           // Don't push a " " in the textContentItem
           // (except when it's between two non-spaces chars),