Revert "take out unused variables"

This reverts commit e5752ff9b3.

The variables i and n are used in the `#if !__GLIBC_PREREQ(2, 7)`
branch.

Closes gh-1586.

driver/others/memory.c

@@ -180,7 +180,7 @@ int get_num_procs(void) {
 cpu_set_t *cpusetp;
 size_t size;
 int ret;
-// int i,n;
+int i,n;
 
   if (!nums) nums = sysconf(_SC_NPROCESSORS_CONF);
 #if !defined(OS_LINUX)