Implement new array function array_column()

array_column() returns the values of the specified column from a
multi-dimensional array.
Adding tests for the negative results of array_column()
Adding test for columns not present in all rows for array_column().
Simplify the code and use zend_hash_next_index_insert()
Fixing typo in test for array_column()
array_column: Cleaning up, as recommended in pull request #56 comments
array_column: Improved tests
array_column: Using add_next_index_zval() at nikic's recommendation.
array_column: Adding test for IS_OBJECT and converting object to string
Cleaning up a memory leak.
array_column: Implement ability to specify an index column
array_column: Set array_pluck as an alias for array_column
array_column: Removed array_pluck() alias
Open Source Release
spelling
Fix typos and grammar issues in README.
typo at Optimizer/block_pass.c
Fixed zend_optimizerplus.enable_file_override=1 compatibility with PHP-5.3
Added LICENSE from http://www.php.net/license/3_01.txt

Closes #2
Fix typo