OO-1261: prevent line break in navbar after im message icons

src/main/java/org/olat/instantMessaging/ui/_content/topnav.html

 #if(!$inAssessment)
-	$r.render("newMsgPanel")
+	<div class="o_im_messages">
+		$r.render("newMsgPanel")
+	</div>
 
 	<div id="o_im_status" class="dropdown">
 		<a href="#" class="o_undecorated dropdown-toggle" data-toggle="dropdown" title="$r.translate("im.status.change.long")">

src/main/webapp/static/themes/light/modules/_im.scss

 /* Instant Messaging components in navbar */
 #o_navbar_imclient {
+	.o_im_messages {
+		float: left;
+	}
 	#o_im_message, 	
 	#o_im_status,
 	#o_im_summary {
@@ -19,15 +22,18 @@
 	#o_im_status div.o_chelp_wrapper {
 		right: 0.5em;
 	}
-	#o_im_message .o_icon_message {
-		color: $o-im-newmessage-color;
-		&:hover {
-			color: $o-im-newmessage-hover-color;		
+	#o_im_message {
+		a:hover,
+		a:focus {
+			text-decoration: none;
+		}
+		.o_icon_message {
+			color: $o-im-newmessage-color;
+			&:hover {
+				color: $o-im-newmessage-hover-color;		
+			}	
 		}		
 	}
-	#o_im_messages {
-		float: left;
-	}
 }
 
 .o_im_load_history {