Forward declare some memoryview utility code functions.
Forward declare some memoryview utility code functions.

cython/cython,ChristopherHogan/cython,c-blake/cython,scoder/cython,fabianrost84/cython,cython/cython,scoder/cython,c-blake/cython,fabianrost84/cython,da-woods/cython,ChristopherHogan/cython,da-woods/cython,da-woods/cython,da-woods/cython,fabianrost84/cython,c-blake/cython,c-blake/cython,cython/cython,fabianrost84/cython,cython/cython,ChristopherHogan/cython,fabianrost84/cython,scoder/cython,scoder/cython,c-blake/cython