Add standalone reallocarray.c from OpenBSD instead of rolling our own.

lib/util/alloc.c

@@ -48,7 +48,6 @@
 #elif defined(HAVE_INTTYPES_H)
 # include <inttypes.h>
 #endif
-#include <errno.h>
 #include <limits.h>
 
 #define DEFAULT_TEXT_DOMAIN	"sudo"
@@ -258,17 +257,3 @@ sudo_evasprintf_v1(char **ret, const char *fmt, va_list args)
 	sudo_fatal_nodebug(NULL);
     return len;
 }
-
-#ifndef HAVE_REALLOCARRAY
-void *
-sudo_reallocarray(void *ptr, size_t nmemb, size_t size)
-{
-    if (nmemb > SIZE_MAX / size) {
-	errno = EOVERFLOW;
-	return NULL;
-    }
-
-    size *= nmemb;
-    return ptr ? realloc(ptr, size) : malloc(size);
-}
-#endif /* HAVE_REALLOCARRAY */