message: Support LLVM 16.0/trunk
diff: #define ISPC_LLVM_13_0 130000
  #define ISPC_LLVM_14_0 140000
  #define ISPC_LLVM_15_0 150000
  +#define ISPC_LLVM_16_0 160000
  #define OLDEST_SUPPORTED_LLVM ISPC_LLVM_10_0
  -#define LATEST_SUPPORTED_LLVM ISPC_LLVM_15_0
  +#define LATEST_SUPPORTED_LLVM ISPC_LLVM_16_0
  #ifdef __ispc__xstr
  #undef __ispc__xstr
  __ispc__xstr(LLVM_VERSION_MAJOR) "." __ispc__xstr(LLVM_VERSION_MINOR) "." __ispc__xstr(LLVM_VERSION_PATCH)
  #if ISPC_LLVM_VERSION < OLDEST_SUPPORTED_LLVM || ISPC_LLVM_VERSION > LATEST_SUPPORTED_LLVM
  -#error "Only LLVM 11.0 - 14.0 and 15.0 development branch are supported"
  +#error "Only LLVM 11.0 - 15.0 and 16.0 development branch are supported"
  #endif
  #define ISPC_VERSION_STRING \
  