Issue 1 fix.

Date:       20 August 2013
Details:    Incorrect comparison in dl_exchange() initialisation truth
            statements. Should be DL_SUCCESS, not DLT_SUCCESS.
File:       dllist_test.c
Line:       1026, 1039, 1052
Branch:     master
Priority:   Low
Resolved:   20 August 2013
Issue 2 fix.

Date:       21 August 2013
Details:    The test numbers used in dlt_test_1() are not contiguous. Test
            number 38 is missing from the list.
File:       dllist_test.c
            dllist_test.h
Line:       839, 119
Branch:     master
Priority:   Low
Resolved:   21 August 2013
Issue 3 fix.

Date:       21 August 2013
Details:    The _create_object() function does not return DLT_NO_MEMORY if
            the new_object malloc operation fails.
File:       dllist_test.c
Line:       1274
Branch:     master
Priority:   Medium
Resolved:   21 August 2013
Deque library added.

1.  Added the deque library and its test unit. This provides full
    coverage of the deque codebase, with the exception of testing
    DE_NO_MEMORY function return values.