message: Bumping version to 1.18.0dev
diff: #pragma once
  #define ISPC_VERSION_MAJOR 1
  -#define ISPC_VERSION_MINOR 17
  -#define ISPC_VERSION "1.17.0"
  +#define ISPC_VERSION_MINOR 18
  +#define ISPC_VERSION "1.18.0dev"
  #include <llvm/Config/llvm-config.h>
  #define ISPC_LLVM_VERSION (LLVM_VERSION_MAJOR * 10000 + LLVM_VERSION_MINOR * 100)
  