Fixed jQuery 1.2.6 mouseleave issue from #920.

Use bind, rather than .mouseleave, because we officially still support
jQuery 1.2.6, which doesn't define a shortcut for mouseenter or
mouseleave.  This was a bug/oversight that was fixed somewhere around
1.3.x.  We can return to using .mouseleave when we drop support for
1.2.6.

NEWS.md

@@ -170,6 +170,9 @@ The base and overlay canvas are now using the CSS classes "flot-base" and
  - Avoided floating-point precision errors when calculating pie percentages.
    (patch by James Ward, pull request #918)
 
+ - Fixed compatibility with jQuery 1.2.6, which has no 'mouseleave' shortcut.
+   (reported by Bevan, original pull request #920, replaced by direct patch)
+
 
 ## Flot 0.7 ##
 

jquery.flot.js

@@ -884,7 +884,14 @@ Licensed under the MIT license.
             // bind events
             if (options.grid.hoverable) {
                 eventHolder.mousemove(onMouseMove);
-                eventHolder.mouseleave(onMouseLeave);
+
+                // Use bind, rather than .mouseleave, because we officially
+                // still support jQuery 1.2.6, which doesn't define a shortcut
+                // for mouseenter or mouseleave.  This was a bug/oversight that
+                // was fixed somewhere around 1.3.x.  We can return to using
+                // .mouseleave when we drop support for 1.2.6.
+
+                eventHolder.bind("mouseleave", onMouseLeave);
             }
 
             if (options.grid.clickable)