Fix for #1124 - fixed donut innerradius hovering trigger

Submitting a fix for issue #1124. 

The original <code>flot.pie.js</code> renamed to <code>jquery.flot.pie.orig.js</code> would fire a pie hover event on a nearby slice when hovering inside the innerradius or whitespace of a donut pie chart. When hovering inside the donut, a hover or highlighting should not occur. Added the fix to the file <code>jquery.flot.pie.js</code>. The bug and fix are shown in a working demo in file <code>bugTest.html</code>. The demo shows the bug in an <code>iframe</code> of file <code>bug.html</code> and the fix is shown in an <code>iframe</code> of file <code>bugfix.html</code>.