Removed further timing differences during SSL message decryption in ssl_decrypt_buf()

New padding checking is unbiased on correct or incorrect padding and
has no branch prediction timing differences.

The additional MAC checks further straighten out the timing differences.
diff --git a/library/sha2.c b/library/sha2.c
index 0245f31..af3a6ee 100644
--- a/library/sha2.c
+++ b/library/sha2.c
@@ -97,7 +97,7 @@
     ctx->is224 = is224;
 }
 
-static void sha2_process( sha2_context *ctx, const unsigned char data[64] )
+void sha2_process( sha2_context *ctx, const unsigned char data[64] )
 {
     uint32_t temp1, temp2, W[64];
     uint32_t A, B, C, D, E, F, G, H;