Zen's use of "$legacy-support-for-ie{6,7,8}" variables UNSUPPORTED in compass v1.0.0x

When using compass compiler, in order to use current flexbox mixin, you need to update to next-version compass,

	gem install compass --pre

	gem query --local | egrep -i "sass|compass"
		compass (1.0.0.alpha.18)
		compass-core (1.0.0.alpha.17)
		compass-import-once (1.0.2)
		sass (3.3.0.rc.3)
		sass-mediaqueries-rails (1.3)

Once that's done, compiling SASS in a Zen subtheme,

	Core      System (system)         Module  Enabled        7.26           
	Other     Zen (zen)               Theme   Disabled       7.x-5.4        	

reports

	Feb 10 15:28:17 ixybox compass[13509]: #033[31mWARNING: Compass has changed how browser support is configured. See the CHANGELOG for more details. The following configuration variables are no longer supported: $legacy-support-for-ie6, $legacy-support-for-ie7, $legacy-support-for-ie8.

those UNsupported variables are found in Zen @

	cd sites/all/themes/zen/STARTERKIT
	grep -rlni legacy-support-for-ie
		sass-extensions/zen-grids/stylesheets/zen/_grids.scss
		sass-extensions/zen-grids/templates/unit-tests/test-results/zen-nested-container.css
		sass-extensions/zen-grids/templates/unit-tests/test-results/zen-grid-item-base.css
		sass-extensions/zen-grids/templates/unit-tests/test-results/zen-grid-container.css
		sass-extensions/zen-grids/templates/unit-tests/sass/zen-nested-container.scss
		sass-extensions/zen-grids/templates/unit-tests/sass/zen-grid-item-base.scss
		sass-extensions/zen-grids/templates/unit-tests/sass/zen-grid-container.scss
		sass-extensions/zen-grids/templates/project/_init.scss
		sass-extensions/zen-grids/templates/project/_visually-hidden.scss
		sass/_normalize.scss
		sass/_normalize-rtl.scss
		sass/components/_misc.scss
		sass/components/_misc-rtl.scss
		sass/_init.scss
		sass/_mixins.scss