Replace the last strcasecmp with OPENSSL_strcasecmp.

strcasecmp is locale-sensitive, which can cause some mishaps.

This CL should be a no-op, because this call is only used on Android,
and bionic's strcasecmp seems to be ASCII-only. But using
OPENSSL_strcasecmp everywhere is easier to reason about.

Change-Id: Iecf9bc4da1bb3a4ab87b1e8b1d7f6f6c6e44aceb
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/52305
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>

crypto/fipsmodule/rand/urandom.c

@@ -135,7 +135,7 @@ static void maybe_set_extra_getrandom_flags(void) {
   }
 
   value[length] = 0;
-  if (strcasecmp(value, "true") == 0) {
+  if (OPENSSL_strcasecmp(value, "true") == 0) {
     *extra_getrandom_flags_for_seed_bss_get() = GRND_RANDOM;
   }
 #endif