Claro/RTL: TabContainer: close button not visible IE7 or IE quirks high contrast

[bill]

The close button is not visible when themeTester.html?dir=rtl is run on IE7 or themeTeststerQuirk.html?dir=rtl run on IE, presumably due to this weird rule in claro/layout/TabContainer_rtl.css:

.dj_ie7 .claro .dijitTabRtl .dijitTabCloseText,
.dj_iequirks .claro .dijitTabRtl .dijitTabCloseText {
	width: 0;
	height: 0;
	overflow: hidden;
	float: left;
}

[bill]

(In [22187]) Fix a number of TabContainer issues related to close icon:

• no [x] text appears in IE7 or IE quirks high-contrast RTL mode (fixes #11153)
• icon appears on left rather than right in RTL mode
• hover effect broken in tundra, soria, nihilo (regression from [21144], refs #10613)
• height problems mixing closable and unclosable tabs on webkit (fixes #11155, !strict):
  • border under unselected tabs also appears under selected tab
  • closable tabs are 1px too tall, obscuring that same border
• hovering close button in high-contrast mode causes tab to expand horizontally

The main change was to make the close icon a sibling of the label, rather than nested inside of the closeButton span. This avoids browser bugs on webkit and IE. Also stopped using an <img> tag to display the icon since that has issues with the title/alt attributes on IE6/7.