MEMBEROF: silence compilation warnings
    
    src/ldb_modules/memberof.c: In function ‘mbof_get_ghost_from_parent_cb’:
    src/ldb_modules/memberof.c:3085: warning: declaration of ‘dup’ shadows a global declaration
    /usr/include/unistd.h:528: warning: shadowed declaration is here
    src/ldb_modules/memberof.c: In function ‘mbof_inherited_mod’:
    src/ldb_modules/memberof.c:3253: warning: declaration of ‘dup’ shadows a global declaration
    /usr/include/unistd.h:528: warning: shadowed declaration is here
    src/ldb_modules/memberof.c: In function ‘mbof_fill_vals_array’:
    src/ldb_modules/memberof.c:3786: warning: declaration of ‘index’ shadows a global declaration
    /usr/include/string.h:489: warning: shadowed declaration is here