Move "@synthesize nameUsedToInstantiate" inside #ifdef

Move "@synthesize nameUsedToInstantiate" to within …
"#ifdef ENABLE_GLOBAL_IMAGE_CACHE_FOR_SVGKIMAGE_IMAGE_NAMED"
block. When ENABLE_GLOBAL_IMAGE_CACHE_FOR_SVGKIMAGE_IMAGE_NAMED
is not defined this property is not defined in the header file.