Remove static output buffers for hash & HMAC functions.

These static output buffers are a legacy from a time before processes
had threads. This change drops support and callers who were depending on
this (of which there are hopefully none) will crash.

Change-Id: I7b8eb3440def507f92543e55465f821dfa02c7da
Reviewed-on: https://boringssl-review.googlesource.com/14528
Commit-Queue: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/crypto/constant_time_test.cc b/crypto/constant_time_test.cc
index 5ae0c37..0ad7192 100644
--- a/crypto/constant_time_test.cc
+++ b/crypto/constant_time_test.cc
@@ -62,7 +62,7 @@
   return b ? CONSTTIME_TRUE_S : CONSTTIME_FALSE_S;
 }
 
-static uint8_t test_values_8[] = {0, 1, 2, 20, 32, 127, 128, 129, 255};
+static const uint8_t test_values_8[] = {0, 1, 2, 20, 32, 127, 128, 129, 255};
 
 static size_t test_values_s[] = {
     0,