Tag a number of globals as const.

Change-Id: I6f334911f153395a2e5e26adfd08912a1d8c558b
Reviewed-on: https://boringssl-review.googlesource.com/2847
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/evp/evp_ctx.c b/crypto/evp/evp_ctx.c
index 6616038..e1c2886 100644
--- a/crypto/evp/evp_ctx.c
+++ b/crypto/evp/evp_ctx.c
@@ -69,7 +69,7 @@
 extern const EVP_PKEY_METHOD hmac_pkey_meth;
 extern const EVP_PKEY_METHOD ec_pkey_meth;
 
-static const EVP_PKEY_METHOD *evp_methods[] = {
+static const EVP_PKEY_METHOD *const evp_methods[] = {
   &rsa_pkey_meth,
   &hmac_pkey_meth,
   &ec_pkey_meth,