function.lisp: Split converter from translator

This is needed to implement array support.  Converter can be used to
set/get/free array element, which is not giarg.
function.lisp: Array get/set/free support
gir-test.lisp: Revise/Add test cases for array support
function.lisp: Support struct/union as array element

Known issue: can not free struct/union array, because it may be
returned and passed to caller.  May need a mechanism to track this
situation in the future.
function.lisp: Hide array length from caller

Generate array length for input parameters automatically.  Do not
return array length for output parameters.
gir-test.lisp: Adjust test cases for hiding array length
Merge pull request #17 from hying-caritas/array-support

Array support