"ImageIO_PNG_Data"'s count always increase after wake up from background

[jinsongK]

step1.i jump to the "Pin Annotations Demo" view then exit to the home view.
step2.click home button,demo will go to the background.then double-click home button,select demo app,and Repeat the previous operation

[jinsongK]

step1:

step2:

[dblock]

This is because we use imageNamed, see this SO question. Generally, these images should just be loaded via imageWithContentsOfFile, eg:

    NSString *australia = [[[NSBundle mainBundle] bundlePath] stringByAppendingString:@"/Maps/australia.png"];
    [mapView displayMap:[UIImage imageWithContentsOfFile:australia]];

I'll change this.

[dblock]

Fix on HEAD, let me know if you find something else.