Combined patch for the more or less obvious issues

Fixed a memory leak in ASN1_digest and ASN1_item_digest.

asn1_template_noexp_d2i call ASN1_item_ex_free(&skfield,...) on error.

Reworked error handling in asn1_item_ex_combine_new:
- call ASN1_item_ex_free and return the correct error code if ASN1_template_new failed.
- dont call ASN1_item_ex_free if ASN1_OP_NEW_PRE failed.

Reworked error handing in x509_name_ex_d2i and x509_name_encode.

Fixed error handling in int_ctx_new and EVP_PKEY_CTX_dup.

Fixed a memory leak in def_get_class if lh_EX_CLASS_ITEM_insert fails due to OOM:
- to figure out if the insertion succeeded, use lh_EX_CLASS_ITEM_retrieve again.
- on error, p will be NULL, and gen needs to be cleaned up again.

int_free_ex_data needs to have a fallback solution if unable to allocate "storage":
- if free_func is non-zero this must be called to clean up all memory.

Fixed error handling in pkey_hmac_copy.

Fixed error handling in ssleay_rand_add and ssleay_rand_bytes.

Fixed error handling in X509_STORE_new.

Fixed a memory leak in ssl3_get_key_exchange.

Check for null pointer in ssl3_write_bytes.

Check for null pointer in ssl3_get_cert_verify.

Fixed a memory leak in ssl_cert_dup.

Fixes #2087 #2094 #2103 #2104 #2105 #2106 #2107 #2108 #2110 #2111 #2112 #2115

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2127)