Babel C, C++, D support for non-homogeneous input tables

Babel C, C++, D support for non-homogeneous input tables

        * ob-C.el: handling of non-homogeneous tables,
        support for table header,
        support for iterating over table cells.
        (org-babel-expand-body:C++): uncomment
        (org-babel-C-execute): cosmetic changes
        (org-babel-C-expand-C): add support for table columns names,
        add support for table dimensions,
        add standard includes
        (org-babel-C-val-to-C-type): rewrite to support non-homogeneous
        tables cells
        (org-babel-C-table-sizes-to-C): new function to gain access
        to the table dimensions
        (org-babel-C-utility-header-to-C):
        (org-babel-C-header-to-C): new functions to generate
        support for table header.

        * ob-C-test.org: added D sibling tests similar to C++,
        added non-homogeneous table example for C++ and D

        * test-ob-C.el: new tests for D and non-homogeneous tables
        (ob-C/simple-program):
        (ob-C/simple-program):
        (ob-D/simple-program):
        (ob-C/integer-var):
        (ob-D/integer-var):
        (ob-C/two-integer-var):
        (ob-D/two-integer-var):
        (ob-C/string-var):
        (ob-D/string-var):
        (ob-C/preprocessor):
        (ob-C/table):
        (ob-D/table):
        (ob-C/list-var):
        (ob-D/list-var):
        (ob-C/vector-var):
        (ob-D/vector-var):
        (ob-C/list-list-var):
        (ob-D/list-list-var):
        (ob-C/inhomogeneous_table):
        (ob-D/inhomogeneous_table): add compiler availability check
        (ob-D/simple-program):
        (ob-D/integer-var):
        (ob-D/two-integer-var):
        (ob-D/string-var):
        (ob-D/table):
        (ob-D/list-var):
        (ob-D/vector-var):
        (ob-D/list-list-var):
        (ob-D/inhomogeneous_table): add D unit tests
        (ob-C/inhomogeneous_table):
        (ob-D/inhomogeneous_table): add non-homogeneous table
        unit tests