message: c_example: fix warnings, improve output for beginner user
  This commit:
  fixes an unused-variable on "c" array
  Makes whitespace consistent to tabs
  Adds [c_example] prints to output to show beginners where what parts
  of the info logs are coming from.
diff: @@ -11,8 +11,8 @@ int pcm_getcpu()
  "mov %%ecx, %0\n\t":
  "=r" (id) :: "%rax", "%rcx", "%rdx");
  // processor ID is in ECX: https://www.felixcloutier.com/x86/rdtscp
  - // Linux encodes the NUMA node starting at bit 12, so remove the NUMA bits
  - // when returning the CPU integer by masking with 0xFFF.
  + // Linux encodes the NUMA node starting at bit 12, so remove the NUMA
  + // bits when returning the CPU integer by masking with 0xFFF.
  return id & 0xFFF;
  }
  @@ -41,9 +41,12 @@ uint64_t pcm_c_get_core_event(uint32_t, uint32_t);
  int main(int argc, const char *argv[])
  {
  int i,a[100],b[100],c[100];
  + uint32_t total = 0;
  int lcore_id;
  - for (i=0; i < 100; ++i)
  - {
  +
  + /* Seed for predictable rand() results */
  + srand(0);
  + for (i=0; i < 100; ++i) {
  a[i] = rand();
  b[i] = rand();
  c[i] = rand();
  @@ -94,12 +97,19 @@ int main(int argc, const char *argv[])
  return -2;
  }
  + printf("[c_example] Initializing PCM measurements:\n");
  PCM.pcm_c_init();
  +
  + printf("[c_example] Calling PCM start()\n");
  PCM.pcm_c_start();
  for(i=0;i<10000;i++)
  c[i%100] = 4 * a[i%100] + b[i%100];
  + for(i=0;i<100;i++)
  + total += c[i];
  PCM.pcm_c_stop();
  + printf("[c_example] PCM measurment stopped, compute result %u\n", total);
  +
  lcore_id = pcm_getcpu();
  printf("C:%lu I:%lu, IPC:%3.2f\n",
  PCM.pcm_c_get_cycles(lcore_id),
  