[Sass] Fix a bizarre parser error with SCSS and interpolation.

lib/sass/script/lexer.rb

@@ -149,10 +149,10 @@ module Sass
       # @return [Boolean]
       def whitespace?(tok = @tok)
         if tok
-          @scanner.string[0...tok.pos] =~ /\s$/
+          @scanner.string[0...tok.pos] =~ /\s\Z/
         else
           @scanner.string[@scanner.pos, 1] =~ /^\s/ ||
-            @scanner.string[@scanner.pos - 1, 1] =~ /\s$/
+            @scanner.string[@scanner.pos - 1, 1] =~ /\s\Z/
         end
       end
 

test/sass/scss/scss_test.rb

@@ -970,6 +970,21 @@ SCSS
 flim {
   && {a: b}
 }
+SCSS
+  end
+
+  # Regression
+
+  def test_weird_added_space
+    assert_equal <<CSS, render(<<SCSS)
+foo {
+  bar: -moz-bip; }
+CSS
+$value : bip;
+
+foo {
+  bar: -moz-\#{$value};
+}
 SCSS
   end
 end