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
array_column: Fix compile-time warnings
- add new interpolation method
  . imagescale
  . imageaffine
  . replace imagerotate with new generic and optimized new implementations
  . imagesetinterpolationmethod, to set the default interpolation to be
    used with the new functions
  . add imagepalettetotruecolor
- config.m4 sync with .w32
- add new files for interpolation
- fix unix build
- add affine matrix helper for translate, scale, rotate and shear
- add imageaffinematrixget and imagematrixconcat