Fix typo

[hyongtao-code]

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There are 2 vars, compressionOverrunLen and maxBufferWithCompressionOverrrunLen in the definition of struct AppendOnlyStorageWrite. The two variables are related, but spelled differently. I think there is a redundant letter R in maxBufferWithCompressionOver R runLen.

typedef struct AppendOnlyStorageWrite
{
        /*......*/
	/*
	 * Number of bytes of extra buffer must have beyond the output compression
	 * buffer needed for spillover for some compression libraries.
	 */
	int32		compressionOverrunLen;

	/* The maximum buffer plus compression overrun byte length */
	int32		maxBufferWithCompressionOverrrunLen;
        /*......*/
}