Description:
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when you do an imagecopy to a destinationXY which is out of 
range from your destination image, there is no 
error/warning. Fix is simple, just check imagesx and 
imagesy if destinationXY(+width/height) is still in range 

Reproduce code:
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$tile = imagecreate(30,30);
imagecopy($tile, $origim, 999, 999, 100, 100, 50, 50);


Expected result:
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warning, that 999x999 is out of range for a 30x30 image 

Actual result:
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ignored, copied into oblivion