add test coverage for allocation failures in clone-function default tip

fix hash map not being able to deal with 64-bit hashes

add documentation for cxListClone() - relates to #744

add documentation for cxMapClone() - resolves #743

add tests for cxMapClone() - relates to #743

add destruction of uninitialized entries on allocation failure to cxMapClone() - relates to #743

untested draft of cxMapClone() - relates to #743

add cxListClone() - resolves #744 except for test coverage

fix accidental additions of unnecessary unistd.h includes

fix overlooked renaming of cx_attr_export to CX_EXPORT

(0) -1000 -300 -100 -10 tip

mercurial