orcarray: Fix compiler warning with gcc 4.9

orcarray: Fix compiler warning with gcc 4.9

In file included from ../orc/orcprogram.h:5:0,
                 from ../orc/orc.h:5,
                 from ../orc-test/orctest.h:5,
                 from orcarray.c:6:
../orc/orcutils.h:124:37: error: 'data' may be used uninitialized in this function [-Werror=maybe-uninitialized]
 #define ORC_PTR_OFFSET(ptr,offset) ((void *)(((unsigned char *)(ptr)) + (offset)))
                                     ^
orcarray.c:42:9: note: 'data' was declared here
   void *data;