Print out C development environment info

environs.c

// prints local development environment information
void environs() {
#ifdef __clang_major__
    printf ("clang detected version %d.%d\n", __clang_major__, __clang_minor__);
#endif

#ifdef __GNUC__
    // note that clang 3.7 declares itself as a gcc 4.2"
    printf ("gcc detected version %d.%d\n", __GNUC__, __GNUC_MINOR__);
#endif
#if __STDC_VERSION__ >=  201710L
    printf("We are using C18!\n");
#elif __STDC_VERSION__ >= 201112L
    printf("We are using C11!\n");
#elif __STDC_VERSION__ >= 199901L
    printf("We are using C99!\n");
  #else
    printf("We are using C89/C90!\n");
#endif
}