Having more than one automatic local breaks the header generation

[Pekka Jääskeläinen]

<stdin>:8:24: warning: excess elements in scalar initializer
unsigned _local_size = _test_kernel_LOCAL_SIZE;
                       ^~~~~~~~~~~~~~~~~~~~~~~
./.clckQfN7fq/kernel_header.h:5:37: note: expanded from macro '_test_kernel_LOCAL_SIZE'
#define _test_kernel_LOCAL_SIZE {4, 8}

due to

#if _${kernel}_NUM_LOCALS != 0
unsigned _local_size = _${kernel}_LOCAL_SIZE;
#endif

in pocl-kernel.in.

It should assign the sizes to an array, not a scalar.